Okay, that was easy. It still doesn't give me what I want though.
I want a dropdown of nominal dimensions (which the user would know) but I want it to show real dimensions (which the user may not know)
For example, a 2x4 piece of lumber is actually 1.5 x 3.5.
I want them to see "2x4" in the dropdown but when chosen, "1.5x3.5" will appear in the field. Is that possible?