javascript on older version of pocketpc

I am trying to write a javascript that zeros out input fields when a button is pressed.  This code works fine in my development system, but when I try to hit the site from pocket PC (Version 4.20.0), I get an error indicating:
Microsoft JScript runtime error
Line 3: Character: 0
Error: Object doesn't support this property or method
Source: (null)

I have tried many variations, but I believe I may be having problems because the level of DOM supported is 3.02.  Can anyone give me pointers on how to make this script work on this version of DOM?

Sorry, updating the pocket PC version is not an option... :(

<script type="text/javascript">
function zeroit(doc){
    doc.all['form1:tableEx2:0:text5'].value="0";
    doc.all['form1:tableEx2:1:text5'].value="0";
    doc.all['form1:tableEx2:2:text5'].value="0";
    doc.all['form1:tableEx2:3:text5'].value="0";
    doc.all['form1:tableEx2:4:text5'].value="0";
    doc.all['form1:tableEx2:5:text5'].value="0";
    doc.all['form1:tableEx2:6:text5'].value="0";
    doc.all['form1:tableEx2:7:text5'].value="0";
    doc.all['form1:tableEx2:8:text5'].value="0";
    doc.all['form1:tableEx2:9:text5'].value="0";
    doc.all['form1:tableEx2:10:text5'].value="0";
    doc.all['form1:tableEx2:11:text5'].value="0";
    doc.all['form1:tableEx2:12:text5'].value="0";
    doc.all['form1:tableEx2:13:text5'].value="0";
    doc.all['form1:tableEx2:14:text5'].value="0";
}
</script>
 
<hx:commandExButton type="submit" value="Fill with zeros" styleClass="largeCommandExButton" id="button1" onclick="zeroit(this.document)" ></hx:commandExButton>

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