Basic 3.0 question re movieclips and main timeline

1

In my main timeline, outside a function, I set a variable:
var myVariable:String = “MyName”;

I can’t figure out how to change the value of myVariable when I’m in a movieclip

I’ve unsuccessfully tried:
myVariable = “SomethingElse”;
_root.myVariable = “SomethingElse”;
_parent.myVariable = “SomethingElse”;

Also, when I’m in the movieclip (“myMovie_mc”) I can’t figure out how to get out of the clip and go to the main timeline frame labeled “myFrame”

I’ve unsuccessfully tried:
parent.myMovie_mc.gotoAndPlay(“myFrame”);

stage.gotoAndPlay(“myFrame”);

Any help with these basic concepts would be appreciated.