accessing hidden field

[forumdata]

Hello,
Here is some sample code from my html page:
<script language="javascript" type="text/javascript">
function setProperties(formElement)
{
formElement.form.elements["customerID"].value=1;
alert(formElement.form.elements["customerID"].value);


}
</script>

<form name="myform" action="...">
<input type="hidden" name="customerID" id="customerID" value="xxx">
<input type="submit" id="loadform" name="loadform" onClick="setProperties(this);" value="Load form"></input>
<input type="submit" id="process" name="process" value="process"></input>
</form>
There are two submit buttons and I would like to change the hidden field value for one of the buttons when it is clicked. I have tried various ways to assign a value to the hidden field in the javascript but none of them works including the above.
I have tried "formElement.form.customerID.value", "formElement.form.getElementById("customerID"); etc but it does not work. Can someone please guide as to the right way of assigning the hidden field value in javascript. Thanks for your help.

[Fang]

document.getElementById("customerID").value = 'foo';