Accessing variable of parent from string?

programming flash
1

I understand that in AS3 if you want to access a variable in a parent movie from a child you use:

(this.parent as MovieClip).my_variable

but what if you wanted to access a variable from a string?
EX:

var varString:String = "myVar";
(this.parent as MovieClip)[COLOR=Red].varString[/COLOR] ???

[COLOR=Black]
I have tried:
[/COLOR]

(this.parent as MovieClip).this[varString]

[COLOR=Black]
but it doesn’t seem to work. Help would be greatly appreciated.

[/COLOR][COLOR=Black]

[/COLOR]