I can think of several different ways to answer that depending on what results you want.
Do you want all records that contain both selected values or all records that contain one or the other value?
If I could put it this way, the product catalog contains tee shirts from several suppliers. I would like to do a search on the phrase "tee shirts" in my product field and select more than 1 supplier (sometimes), the found set would be all "tee shirts" from the selected suppliers.
That appears to be searching on one value in the value list: "Tee Shirts" instead of two as you originally posted.
You can do this, but the details will vary quite a bit--depending on how you've designed your tables and what you want on your layout.
I'm guessing here that you want to select from a value list of keyword phrases to find every record where its product field contains that keyword phrase.
Option 1: You can create a layout just for performing finds and format your product field with this value list in a drop down. You can set the field's behavior so that it can only be entered in find mode. Then you can set up a button with a script that switches to this layout and enters find mode. You'd then select "tee shirt" from the product field's drop down and perform the find or continue the script so that it can perform the find and then return you to the original layout.
Option 2: Define a global text field and set it up with this drop down.
Write a script:
Enter Find Mode
Set FIeld [YourTable::ProductName ; YourTable::GlobalField]
Set Error Capture [on]
Perform FInd 
This script can be attached to a button next to the global field or you can use a script trigger on the global field to fire the script when the field is exited (Drop down) or modified (pop up).