Query_String is empty in a iFrame

I am trying to build dynamic keywordlist with iframes.But I have problem to transfer the Querystring to the form I load in the iframe.

In the event ‘OnChange’ on my keyword I execute following

url.

st = this[this.selectedIndex].text;

document.all(‘HidFrame [delete: lookupframe]’).src= ‘/Lookup.NSF/departmentlookup?ReadForm&Depart=’ + st;

In my iframe the Querystring only contains ‘ReadForm’.

What I am missing.