Chrome window.returnValue

[windows_mss]

Hi Experts

In my project i used one javascript function to return value form popup window ,

window.returnValue = str;
window.close();

its working fine in IE & Firefox but not in chorme getting undefined,

when i put window.returnValue in the alert of popup window i'm getting value in alert box

i'm calling the page like var opPage = window.showModalDialog(URL, '');

in the parent window when put opPage in alert getting undefined.

this working well in both IE & Firefox but not in Chrome

guidance needed,

thanks in advance