I would like to create a value list that has, for instance, only the Products sold by the Manufacturer selected in another field in the record. Perhaps there is a way to use a conditional function in a find. Can I store the value from the Manufacturer field in a variable, and then generate a value list of Products 'on the fly' (by doing a find on that variable) to make a pop-up menu for the Products field? I'd like to have this kind of functionality when entering a new record. Any suggestions?

look for "conditional value list" in the forums. There are lots of good answers... this is a very popular question.

Far be it from me to persuade someone to not use these forums, but the manual is a good thing to read also!

FileMaker offers conditional value lists as an out-of the box feature, but they are based on relationships rather than 'finds', and they display an index of related values. It's a powerful feature, requiring (in the case of your example) a relationship based on manufacturer (which can be to a second file or a self join relationship - connecting the file to itself).

Once the relationship is in place, you will be able to create a value list, select the option to use values from a field, and then, within the resulting dialog, you will be able to choose an option to include 'only related values'. The result will be that the products displayed on your list will be only those that are associated (via the relationship) with the manufacturer selected on the current record.