AS3 help

I am getting an error with the following code:

[COLOR=Red]this.footerUp = false;[/COLOR]

//User has clicked on footer to move up
function footerUp(p_event : Event) {
if(this.footerUp == false){
Tweener.addTween(this.footerContainer.footerTopBar, {time:0.5, y:this.footerContainer.footerTopBar.y-40});
Tweener.addTween(this.footerContainer.pullUp, {time:0.5, y:this.footerContainer.pullUp.y-40});
Tweener.addTween(this.footerContainer.footerText, {time:0.5, y:this.footerContainer.footerText.y-40});
[COLOR=Red] this.footerUp = true;[/COLOR]
} else {
Tweener.addTween(this.footerContainer.footerTopBar, {time:0.5, y:this.footerContainer.footerTopBar.y+40});
Tweener.addTween(this.footerContainer.pullUp, {time:0.5, y:this.footerContainer.pullUp.y+40});
Tweener.addTween(this.footerContainer.footerText, {time:0.5, y:this.footerContainer.footerText.y+40});
[COLOR=Red] this.footerUp = false;[/COLOR]
}
}

the error is:

1168: Illegal assignment to function footerUp.

It is refering to the lines in red

Any ideas why?