You should really list the name of the module so we can look it up on CPAN to check the syntax :-).

Presumably something is sanity checking what it's writing out; do you have a sheet called `Sales' in the source?

Put debugging statements in; print to standard output the row column and value for each iteration, and you will see where in the source spreadsheet the problematic value is. The Perl debugger (see perldebug) is an invaluable tool for hunting down messages that might not make any sense on first inspection.

Otherwise, there's not enough code here to help - how are you making sure that `Except for cells with formulas (in this case text) that link to another worksheet' - do you do that in your code? Let's see the line of code! Perhaps that's the problem.

Good Luck,
Bug Powder Dust and $_.