Hi Marty,
Welcome to Bytes!
What you're talking about is called cascading combo boxes. Click
HERE for a tutorial on how to set them up.
If you've got two tables, Product Types and Product Names, you just need to make sure that there's some way to identify the Product Type from the Product Name table. So, if you've got a column in your Product Names table for the name of the product (I know, duh!), and it says "Coke", you'll need another column for the Product Type, which I would name ProductTypeFK (the FK stands for foreign key in case that's a foreign term, excuse the pun).
So, what the heck is a foreign key? It's a reference value that you include in one table in order to create a relationship, or link with another table's primary key. A primary key is a unique identifier for your table.
In your Product Types table, you might have ProductTypeID as your primary key, then have all of the other fields as regular attributes. Your primary key, if you do as I've suggested, would be an autonumber field.
In your Product Names table, as I mentioned before, you'll want to add a foreign key. The foreign key, if you do as I've suggested, will be a regular number field.
Then, you'll want to go into the Datasheet mode for your Product Names table and enter the corresponding number from the Product Types table in your ProductTypesFK field.
The last step is to create the relationship between the tables. Go to Tools -> Relationships, add both tables, then click and drag the ProductTypeID field from your Product Types table to the ProductTypeIDFK field on your Product Names table. After you do this you'll get a pop up...put a check mark in the box next to "Enforce Referential Integrity" (you can look this up online if you want to find out more about it).
Once you've gotten this far you can use the link I supplied and get to work on your form.
Good luck,
beacon