Can you provide an example of what you are trying to do. and what role is played by the "wildcards".
FileMaker has quite a few text functions, including the position and pattern count functions that can search the text in a field, but the role of those wildcards may be a major issue here that makes it necessary to use a Custom Function (requires Filemaker Advanced to install the function) or a script to do the necessary substitution.
I would have a line of text in a description field that says "(Cat. #AB123456)". The text will vary after the "#". It can be located anywhere within the description and would even show up mutliple times. I have a better understanding of Excel and Access than I do FileMaker Pro. So I built the formula in Excel first to see if I could then work it into FileMaker. I wouldn't mind just working out of Excel and just importing it into FileMaker, however, another person has to run the script that doesn't have Excel experience.
Ok, but what do you want to do with that text once each instance is located within that field?
You may have a very good understanding of what your excel functions do, but I am not familiar with the ones you are using here so I need more explanation before I can spell out a way to do this in FileMaker.
You may want to take a look at the Find/Replace function that can be performed from the Edit menu or in a script as a way to get the results that you need here.
The text will vary after the "#"
Will the number of characters after the # be the same or will that also vary?