This variable is driving me nuts!!

I've initialized a variable on the main timeline:
var varCourse:String = "incomplete";

From within a movieclip's (mc_myMC) timeline, I change my variable as follows:
this._parent.varCourse = "completed";

I return to the main timeline and want to display a message (mc_Message) based on my varCourse value. I realize that each time I enter the main timeline, varCourse is reset to "incomplete" so I will never be able to display mc_Message based on my varCourse value being changed to "completed" in mc_myMC. I can't initialize varCourse elsewhere in my file because I'm already at _root. How do I keep the value of varCourse from being reset to "incomplete" upon returning to the main timeline?

Thanks.