Hi Jase,

Is the supplier ID required for some reason (i.e. is it used in
formulas or something)? I'm assuming there's a reason why you can't
simply delete the codes before distribution and put them back later
based on some other criteria. I'm assuming you know you can hide
columns and/or use a format of ";;;" or set the font to white so the
cell looks empty. This is obviously not very secure, but just some
options.

If you want anything half-way secure ... you'll need code (macros as
you described). I say "half-way" because Excel is not very secure
even if you password protect your code. If an expert really wants to
decifer your Excel file they can ... and very quickly I might add ...
there are better solutions than Excel if security is really critical.

I'm no security expert, but in the past I've used some custom VBA
functions w/ psuedo random sequences to create unique codes as you
described. Then a secret "seed" can be used to decipher what the
orginal code was. As you can imagine, this can get complex and is
still relatively easy to decipher. Frankly, why make this so complex?
Guess I'm missing something.

Why don't you simply substitute the supplier codes with something only
you know the meaning of? Change your formulas if necessary. Example:
say your supplier is Microsoft (MSFT). Change "MSFT" in your sheet
to "A" or "1" ... whatever. If necessary convert the temp codes back
when the customer returns the file to you. This is simple and
probably doesn't even need to be automated, although it could be with
code.

Hope this helps and gives you some ideas.

Regards,
Steve Hieb