Nope, doesn't seem to work.
What I tried is this:
onClose="javascript: <? echo "window.open('csc_logout.php?csr_id=$csr_id', 'csc_logout', 'width=600,height=200,resizable=no,scrollbars=no,toolbar=no,location=yes');"
Wanting it to open that URL in a new window on closing the current window. It works with onUnLoad, but that's not what I want.