How to resize a popup window

Hi,

I want to resize the Task pop up when I create a task from an Entity. New activity --> Task

I have included this lines in the onload event:

alert(screen.availWidth +"-"+ screen.availHeight);

window.resizeTo(screen.availWidth, screen.availHeight);

the pop up if opened, the alert is showed but it is not resized... any ideas??

thanks