# Mod 43 Check Digit calculator

C

#### CLI-Art

Is there a mod43 check digit calculator in Excel. If not, has anyone out

O

R

#### Rick Rothstein

Does this formula do what you want?

=MOD(SUMPRODUCT(SEARCH(MID(A1,ROW(1:99),1),"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-.
\$/+%") )-99,43)

I think it calculates the MOD43 check number for the text in A1. If you need
the formula to calculate the character equivalent to this number, then try
this formula...

=MID("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-.
\$/+%",MOD(SUMPRODUCT(SEARCH(MID(A1,ROW(1:99),1),"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-.
\$/+%") )-99,43),1)

N

#### Nigel

Here is a UDF. Add it to a standard code module and use formula in cell.
e.g.

=ModFT("123") as a direct conversion of some text or
=ModFT(A3) as a range reference

Const charSet As String = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. \$/+%"
Function ModFT(sValue As String)
Dim i As Integer, T As Long
For i = 1 To Len(Trim(UCase(sValue)))
T = InStr(charSet, Mid(sValue, i, 1)) - 1 + T
Next i
ModFT = sValue & Mid\$(charSet, (T Mod 43 + 1), 1)
End Function

C

#### CLI-Art

Perhaps I am not gettting this into my file correctly but it does not seem to
be working correctly. Should I just copy the entire string into the first
cell and go from there?

C

#### CLI-Art

I am a newer user to excel and this post has me lost. Can you "dumb" it up a
bit?

R

#### Rick Rothstein

First off, since you will probably want to copy the formula down the column,
I left off a couple of needed absolute references. Use this formula instead
of the one I posted originally...

=MOD(SUMPRODUCT(SEARCH(MID(A1,ROW(\$1:\$99),1),"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-.\$/+%")
)-99,43)

My formula assumes your text is in A1... you would put the above formula in
any other column (in most likely in row 1 of that column to keep the text
and the MOD43 number in sync). If you have more text under A1 that you want
the MOD43 number for, then just copy my formula down through those rows. If
your text strings are in a different column, then change the A1 reference in
my formula to the first cell in the column the text is in. For example, if
your first text string is in E3, then the above formula would become this...

=MOD(SUMPRODUCT(SEARCH(MID(F3,ROW(\$1:\$99),1),"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-.\$/+%")
)-99,43)

which you might place in, say, F3.

C

#### CLI-Art

Almost there. The formula seems to be working EXCEPT, it is not replacing
numbers 10 and up with the corresponding alpha characters.

R

#### Rick Rothstein

Which formula are you using... the second one I posted (in my original
response to you) should return the check character itself rather than the
check number. Here is that formula with the absolute reference problem that
I mentioned in my other post fixed...

=MID("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. \$/+%",
MOD(SUMPRODUCT(SEARCH(MID(A1,ROW(\$1:\$99),1),
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. \$/+%") )-99,43),1)

As before, there is a single reference to A1 that needs to be changed to the
address for the first cell containing your data. I just noticed there is a
space in the encoding string at the 39th position. That means if your check
number is 39, then the above formula will return a space which will be "hard
to see". I have also manually broken the formula up in order to stop your
newsreader from using the space character as a point to word-wrap at (which
makes it possible for you, and others reading this thread, to accidentally
erase it when combining the broken lines into a single line formula when
placing it into the Formula Bar).

C

#### CLI-Art

This one seems to be working. Thank you very much for your help. I am
having an additional issue which is somewhat unrelated, but causing a
miscalculation of the check digit. The number that I am adding a mod 43
check digit to is a 16 digit number and in order to get it to serialize in
Excel I had to force the initial 1 in with cell formatting. the first number
is 1000000009000001. If I enter that number as I have typed it here the end
1 changes to a 0 and it does not increment correctly. I have tried numeous
cell formats. Can I modify the formula for this item only and force in the
extra 1

C

#### CLI-Art

I have to take back the working part. The digit seems to be off by 1 even
taking the
missing leading 1 into consideration. for 900001 ( leaving out all of the
leading #s) I get a check digit of 9 and it should be 10 which would be an A.

R

#### Rick Rothstein

Yes, I see what you mean about being one off. This should fix that
problem...

=MID("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. \$/+%",
MOD(SUMPRODUCT(SEARCH(MID(A1,ROW(\$1:\$99),1),
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. \$/+%") )-98,43),1)

As for you 16-digit problem... that is Excel's fault... it can only handle
numbers with 15 significant digits. If you are not using this number for
calculating with, then you can either enter the numbers with a leading
apostrophe (which make the entry a text entry). The other possible way to
solve the problem is to format the column as Text so that Excel won't think
you are entering a number. Either way, you won't need to use a leading 1.
Let us know how that works out for you.

O

#### OssieMac

I think that you should input your numbers as strings. Either format the
column as text or precede the number with a single quote.

N

#### Nigel

UDF = user defined function, that can be used just like standard Excel
functions.

To install this code
Press Alt-F11 and the VBA editor will open. From the menu choose Insert,
then from the drop down click Module.
Copy then paste all of the code shown below.
Close the editor by pressing Alt-Q

To use the UDF, you type the function name e.g

=ModFT

as you would any Excel function, then open bracket

=ModFT(

Then either type the string you are trying to convert by putting in inside
double-quotes, then close brackets

=ModFT("MYSTRING")

or reference another cell with the string you wish to convert, so lets
assume your string is in A1, you can type in B1 the function and reference
to A1

=ModFT(A1)

Every time you change the value in A1 the converted value appears in B1 (in
this example)

' copy from line below to end of copy
Const charSet As String = _
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. \$/+%"
Function ModFT(sValue As String)
Dim i As Integer, T As Long
For i = 1 To Len(Trim(UCase(sValue)))
T = InStr(charSet, Mid(sValue, i, 1)) - 1 + T
Next i
ModFT = sValue & Mid\$(charSet, (T Mod 43 + 1), 1)
End Function
' end of copy

--

Regards,
Nigel

C

#### CLI-Art

Again, thank you very much. Now that I figured a work around for the 16
digit problem I am off to the races. Your help is greatly appreciated!!

#### Allzee

First off, since you will probably want to copy the formula down the column,
I left off a couple of needed absolute references. Use this formula instead
of the one I posted originally...

=MOD(SUMPRODUCT(SEARCH(MID(A1,ROW(\$1:\$99),1),"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-.\$/+%")
)-99,43)

My formula assumes your text is in A1... you would put the above formula in
any other column (in most likely in row 1 of that column to keep the text
and the MOD43 number in sync). If you have more text under A1 that you want
the MOD43 number for, then just copy my formula down through those rows. If
your text strings are in a different column, then change the A1 reference in
my formula to the first cell in the column the text is in. For example, if
your first text string is in E3, then the above formula would become this...

=MOD(SUMPRODUCT(SEARCH(MID(F3,ROW(\$1:\$99),1),"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-.\$/+%")
)-99,43)

which you might place in, say, F3.

Lets say i have numbers 1 to 10 in my spreadsheet and i want to add modulo check digit to them all at once. Whats the formula to automate them unlike going to change the column number in the formula for every number i want to assign the check digit?