ActionScript 2.0 :: ParentVar Not Defined Within MovieClip

The thing is that I have a global var on the main line "Gvar"...so far good ? Next there's a Mc that is supposed to change a variable called "ParentVar" but... the ParentVar is not defined within the Mc but rather it's passed to it by :

OnClipEvent(load) {
ParentVar = _global.Gvar
//the global variable is passed to the Mc
}

Now once the global variable is passed down, at some point in the mc. I want the Mc to change "It's" ParentVar witch in this case is _global.Gvar eg. (ParentVar = "HELLO") and that should change _global.Gvar problem is that this will only change the parentVar and not the global var, the only reason I'm doing this way is that I want to have multiple MC's that changes Multiple Globals while using single Mc instance copies.