I am positive this is missing something obvious but after staring at it for like an hour i have accepted defeat and need help, any input will be much appreciated.

The first image is working the second sadly isnt

PHP Code:
<HTML
<
HEAD>
<
SCRIPT type="text/javascript"
function 
blendTest1(img,which

if (
which="1")
  {
    
Test1.filters.blendTrans.Apply(); 
    
Test1.src img
    
Test1.filters.blendTrans.Play(); 
  }
else if (
which="2")
  {
    
Test2.filters.blendTrans.Apply(); 
    
Test2.src img
    
Test2.filters.blendTrans.Play(); 
  }



</script> 
</HEAD> 
<BODY> 

<IMG ID="Test1" SRC="a.png" 
STYLE="filter:blendTrans(duration=.5)" 
onmouseout="blendTest1('a.png','1')" 
onmouseover="blendTest1('b.png','1')" 
onmousedown="blendTest1('c.png','1')"
onmouseup="blendTest1('b.png','1')"> <br>

<IMG ID="Test2" SRC="a.png" 
STYLE="filter:blendTrans(duration=.5)" 
onmouseout="blendTest2('a.png','2')" 
onmouseover="blendTest2('b.png','2')" 
onmousedown="blendTest2('c.png','2')"
onmouseup="blendTest2('b.png','2')">

</BODY> 
</HTML>