undefined probs

Hey E

IIS5.0/javascript/IE

har suget dette script og tilpasset det, men får fejlen undefined i 2. select box efter 4 af 5 items listes.

kode:
<script language="JavaScript">

var MA1 = new Array("MA-1-1","MA-1-2","MA-1-3","MA-1-4","MA-1-5");

var MA2 = new Array("MA-2-1","MA-2-2","MA-2-3","MA-2-4","MA-2-5");

var MA3 = new Array("MA-3-1","MA-3-2","MA-3-3","MA-3-4","MA-3-5");

function setSelect(whichForm) {
    subKat = whichForm.s1.options[whichForm.s1.selectedIndex].value;
    subKatArray = eval("window."+subKat);
    whichForm.s2.options.length = 0;
    for (i=0; i=subKatArray.length; i+=1) {
        whichForm.s2.options[whichForm.s2.options.length] = new Option();
        whichForm.s2.options[whichForm.s2.options.length-1].value = subKatArray[i];
        whichForm.s2.options[whichForm.s2.options.length-1].text = subKatArray[i+1];
    }
}
</script>

Skal jeg poste mere kode?