Data validation question

[Fred]

I'd like to create data validation in a cell that prevents
user's from entering any commas, but allowing all other
characters. This spreadsheet is exported to a comma delimited
file, and extra commas cause problems. I looked at the examples
in help, and couldn't find anything preventing a character from
being entered into a cell. Any ideas?

-Thanks

 

[Dave Peterson]

A couple of ways:

=ISNUMBER(SEARCH(A1,","))
or
=COUNTIF(A1,"*,*")=0
or
=LEN(A1)=LEN(SUBSTITUTE(A1,",",""))