You might want to invest in a book or some tutorials on Filemaker. We'll help you all we can, but those resources can help "fill in the background" so that posts here in the forum will make better sense to you.
You have more than one way you can use a drop down to select a set of records that match the value you select.
Here's the simplest:
Define your drop down field as a global field. (When you define the field click the options button and then select the storage tab from the dialog that pops up.)
Format it with your value list on a layout.
Write a script:
Enter Find Mode
Set Field [YourTable::YourProductIDField; YourTable::YourGlobalField]
Set Error Capture [on]
Perform Find 
Sort [No dialog; restore]
Now you can select a value from the value list and run this script to see the matching records sorted in an order you specify in the last step.
If you learn how to set up tables of related records there's also an option for displaying your records in a portal where your drop down acts as a filter to select the records that appear in the portal. If that sounds like a good option to you, read up on portals in the filemaker's help system.
Many new users get confused the first time they try to add Set Field to a script. See the following link for step by step instructions: (Scroll down towards the end of the thread.)
Selecting an "All" option with checkboxes
Ah yeah I am aware I need some tutorials or something, I was suddenly faced with FileMaker in work and I am trying to do my best in the little time that I have!
I will follow your guides and give it a shot, see what happens!!!
Thanks very much for your quick response.