Note: I have zero experience in Flashscript, but...
Not every programming language has (easy) constructs for what you want. Basically you're trying to reference an object by name by joining 2 strings.
In other languages I've used one of 2 methods:
1. create an array (or linked list or whatever) with the objects in question.
2. construct the name of the object (string3=string1+string2) then use a GetObjectByName(string3)
Whichever method is applicable depends on Flashscript, but as I said, I've never programmed in Flash.
At least this post bumps your thread back up. Hope it helps