Red, I am assuming you are joining data from a report with your zip code data in an Access database. (is that correct?)
There might be some trailing spaces after some of your customer numbers. Try this: In your Monarch model, try this calculated field (we'll call it "Trimmed Customer Number"):
RTRIM(enter name of your customer number data field name here)
RTRIM is a function that will "trim", or remove, any trailing spaces for a field of data.
Now redefine your Data Join by specifying the "Trimmed Customer Number" as the Join Column from your report data, to the customer number column in your Access file. Let me know if this worked.
Mike, thanks for you help, it did get me going in the right direction. What I figured out was that the trap I was using on the template to pull the customer number & zip out had a problem. Once I fixed that everything cleared up. However, I did leave the RTRIM in place since I could see were a user inputting only a 5 digit zip code could put additional spaces in a field sized for a 9 digit zip code- Red