Simple variable question

take a look at the results of these traces:

  trace(imgGal);  //traces "1"
  trace(itemClip1._y);   //traces "32"
  trace(itemClip[imgGal]._y);   //traces "undefined"

why does the last trace not trace “32” like the second trace? I want to insert the variable “imgGal” onto the end of the mc “itemClip”, how can I do this?

this is what I want it for:
[indent]arrow._y = itemClip[imgGal]._y + 8;