I have an iframe (code below).. what i want to check is whether this iframe has lloaded or not and if not loaded load another page(by javascript checking in main page)

<div style="font-family:Georgia, "Times New Roman", Times, serif">
<IFRAME NAME="mainframe" id="mainframe"  FRAMEBORDER=0 MARGINWIDTH=0 MARGINHEIGHT=0 SCROLLING=NO WIDTH=580 HEIGHT=100  style="position:relative; left:16px; margin-top:90px;" onload="genurl1('/cgi-bin/nph-gov.cgi')"></IFRAME>
What im trying to do is make the iframe call a function in main page (which on call assigns a value to a variable.and if that variable is set i can know the page has loaded and if that variable is not set ,the iframe has not loaded)

NOTE:the iframe src is from another domain

I need help on gng about doing this. ...as the iframe src is another domain and will i be able to call a function in in main page thru the iframe..and assign a value.