Image Swapping
 

I want to swap two images back and forth based on a mouse click. eg + and -.
i am doing this on a tree structure based on the values extracted from the database.
eg

+ English
- Maths
- Trignometry
+ Chemistry

and the code which i am using is

<script language='javascript' type='text/javascript'>

intImage = 2;

function swapimage() {

switch (intImage) {

 case 1:

   imgname.src = "plus.gif"

   intImage = 2

   return(false);

case 2:

   imgname.src = "minus.gif"

   intImage = 1

   return(false);

 }

}

</script>

Now the problem is that i am only able to do this image swapping on 'English'. But i want this for the entire TREE Structure based on the node which the user clicks.

Please help.....