APEX

Hi,

I have a select list and a hidden item on my page, after select a value, I want to write this value (and a little bit more) to the hidden item.
So I have done the following...

applied to page html header:
<script language="JavaScript" type="text/javascript">
function setExpress(item_id)
{
html_GetElement('P230_HIDDEN').value = 'Test ' + html_GetElement(item_id).value;
}
</script>

and in selection list I set the HTML Form Element Attributes to onChange="setExpress(this.id); .

But nothing is written to the hidden item. When I make it a text field it works correct.
Isn't it possible to set a value of hidden item by javascript? Is there another way to do this (without computation)?

Thanks for help
chrissy