Filter related fields

[enquirerfm]

This must be quite easy?

I have 2 files. One is a name, company and address file where reach record is classified according to a category e.g. shipper, marketing,agent,organisation,manufacturer etc. My second file is a table of products: cotton t-shirt, lighter, bowl etc. What I want to do is create various fields in this second file which are drop-downs of the company name found in the first file but only by reference to its category e.g coton t-shirt would have a related field for manufacturer which would only include companies which had been checked as manufacturer using the value field in the first file. Clear? Hope so.