playing animation X on event y

Hi,
I had some code which worked perfectly for simply changing frames.

function xxx::onAdd(%this)
{
	$xxx = %this;
	%this.setUseMouseEvents(true);
	%this.setFrame( 0 );
}

function xxx::onMouseUp(%this, %modifier, %worldPosition, %mouseClicks)
{
	if(%this.Animation == 0)  
       %this.setFrame( 1 );  
   else if(%this.Frame == 1)  
       %this.setFrame( 0 );  
}

what I want to do tho is have the event (mouseUp) trigger an animation instead. SO I thought but simply plugging in the correct data, it would run, not so. Could anyone explain why this code is proving to be illogical (doesn't work).

function xxx::onAdd(%this)
{
	$xxx = %this;
	%this.setUseMouseEvents(true);
	%this.setAnimation(xxxOne);
}

function xxx::onMouseUp(%this, %modifier, %worldPosition, %mouseClicks)
{
	if(%this.Animation = xxxOne)  
       %this.setAnimation( xxxTwo );  
 
}