Using variables in my dot syntax

This feels like a weird problem, but there has to be a way to do it:

This animation I’m working on has a dozen pairs of movie clips (with only two library items, one for each type in the pair) with instance names of the form “x” and “xgoal” (this is a drag and drop thing).

When I’m writing AS for the “x” clip, how can I refer to its “xgoal” generally? I tried something like:

goalName = this._name + “goal”;

And then using the goalName variable in my dot syntax (retrieving the _x coordinate for the goal clip):

this.xgoal = _root.goalName._x;

But, of course, that did not work. How can I get around this?

I can post a highly simplified version of the .fla (the real thing is huge) if it would help clarify my problem.