help with stopping java function per element

I want to stop a rollover function for a particular element in my menu. At the moment I have several functions and I need to control them. If I mouseOver a menu item I need an image to slide in partially and if I mouse out slide back off the screen. If I click the menu item I want the image to slide all the way in but then I want to kill or remove the mouseOut function for that menu item until another menu item is clicked on.

Is it possible to keep a function from working until it's required?

 <script language="javascript" type="text/javascript">  
        //slide in onClick
        var isOut = 'True'       
        function slideIn(id){
           if(isOut == 'True' || id=='home_btn'){
                t1.continueTo(363,2);
                isOut = 'False'
                
                }                       
        }
        /*
        function slideOut(id){ 
          t1 = new Tween(document.getElementById(id).style,'left',Tween.elasticEaseOut,363,995,2,'px');        
          t1.start();                    
        }
        */   
        
        //mouseOut         
        function bounceOut(id){                    
           t1 = new Tween(document.getElementById(id).style,'left',Tween.elasticEaseOut,830,995,1,'px');  
           t1.start();
        }
        
        //mouseOver
        function bounceIn(id){
           Show(id); 
           //alert(isOut)           
           t1 = new Tween(document.getElementById(id).style,'left',Tween.elasticEaseOut,995,830,1,'px');
           t1.start();
        }
      
      //change background images onClick
         function changeBg(id){           
            if(id=='home_btn'){
                //alert('home')
                document.getElementById('page_bg').style.backgroundImage='url(images/home_bg.jpg)';
             }
            
            else if(id=='about_you'){
             //alert('about_you')
                document.getElementById('page_bg').style.backgroundImage='url(images/aboutyou_bg.jpg)';
             }
           else if(id=='raise_bar'){
             //alert('about_you')
                document.getElementById('page_bg').style.backgroundImage='url(images/raisebar_bg.jpg)';
             }
        }
        
    </script>

Code (markup):