Hi Chappies

I'm generating a popup window from flash using the code below:
getURL ("javascript:window.open('duh.html','newWin','width=600,height=500,left=100,top=100, toolbar=No,location=No,scrollbars=Yes,status=No,resizable=No,fullscreen=No');void(0);");
Now I want to be able to centre this window to the middle of the screen. I can do this easily enough If i was to write a javascript function say for an html page, however you can't write javascript functions in flash, just command lines like the one above. So how can I centre this window?
i've tried:
left=((screen.width - 600)/2), top=((screen.height - 500)/2)
but thats doesnt appear to work.

any ideas ?

Many thanks