Help with NPC script.

[Archangel]

ffc script Gibdo2{
		void run(){
				npc Shadow = Screen->LoadNPC(1);
				npc Gibdo = Screen->LoadNPC(2);
				while(????){
						Shadow->X = Gibdo->X + 32;
						Shadow->Y = Gibdo->Y;
						Waitframe();
				}
		}
}

Basically it compiles find if I put true in it. But I want it to loop only if the Gibdo is still alive.
The problem is that when I use Bool isValid method, I can't get it to work. This is what I'm using.

While(bool Gibdo->isValid){

Note: If you have ever played Land Stalker, this gibdo is suppose to function as an exact duplicate of the mummy from the crypt with the 8 puzzles.

EDIT: Okay, so I compiled it, and it works find. The only problem is that the Gibdo warps to combo 2 on the grid meaning the script is continuing. When all is said and done slaying the shadow kills the Gibdo using the ring leader function.