Allowing a condition, only if...

I have this behavior. How it works is that it is a button which, onMouseUp, triggers the dismounting of another object. The trick is I only want the dismount call to work, ONLY if the said other object IS mounted. If it is not mounted, I want the dismount, onMouseUp to not work.

function starDismountBtn::onBehaviorAdd(%this)
{
	%this.owner.enableUpdateCallback();
}

function starDismountBtn::onUpdate(%this)
{
	%this.checkStarMount();
}

function starDismountBtn::checkStarMount(%this)
{
	%starIsMounted = %this.star.getIsMounted();
	
	if(%starIsMounted == flase)
	return;
	
	%this.owner.setUseMouseEvents(true);
}



function starDismountBtn::onMouseUp(%this, %modifier, %worldPos)
{
	%this.star.dismount();
	%this.star.setConstantForceY(%this.gravity);
}