Target movieclip with

i have a movieclip which is added to the stage:

var profileholder:profileHolder=new profileHolder ;

inside of profileholder is another movieclip(infoBtn) that acts as a button.

when the mouse is over profileholder i want to do something with infoBtn like:

//profOver is the over state of profileholder
function profOver(e:Event) {;

this doesn’t work and brings up this error:
ReferenceError: Error #1069: Property infoBtn not found on flash.display.Loader and there is no default value.
at main_fla::MainTimeline/profOver()

i also tried:
function profOver(e:Event) {
var as profileHolder;

and get this error:

TypeError: Error #1009: Cannot access a property or method of a null object reference.