Comparing two columns of dates

[Guest]

I'm working in Excel 2007.

I have two columns of dates, the first being a "buy" date and the second
being a "sell" date for the item in that row. If the data is valid, obviously
each date in the second column should be later than the corresponding date in
the first column.

I'd like to create a function that will compare each date in the first
column to the adjacent date in the second column, and tell me if the data is
valid or if there is a date-pair in which the "buy" date falls after the
"sell" date. I don't need this comparison returned for each pair, I just need
to check the columns as a whole and get a "VALID" OR "INVALID" value.

I'm thinking that this needs to be some sort of composite function, maybe
involving a COUNTIF(), but I just can't figure out how to work it.

Thanks for the help!

 

[T. Valko]

A couple of questions...

Can the sell date be the same as the buy date?

If you haven't sold yet then there probably isn't a sell date entered yet,
correct?

 

[Guest]

No, the sell date can never be the same as the buy date - it should always be
at least a day later.

And every pair is full - there are no missing dates. I.E. every item in this
list has been sold.

 

[T. Valko]

Try this:

=IF(SUMPRODUCT(--(A1:A10<B1:B10))=COUNT(A1:A10),"Valid","Invalid")

Note that you can't use entire columns as range references with SUMPRODUCT
unless you're using Excel 2007.

 

[Guest]

Works like a charm - now I get to play around with it and try and figure out
how it works.

Thanks!

 

[T. Valko]

You're welcome. Thanks for the feedback!