Giving loaded mc a instance name

hi there..

Call me stupid...but how can I give a loaded MC a instance name???

So for example:
_root.holder.loadMovie("externalMC"); >>>how can I give "externalMC" a instance name???

Cheers,



Marvin

var instanceName:MovieClip = _root.holder;

var instanceName:String = "externalMC";
;)