[Javascript] how to change the source propertie of a frame in a window from an other one

[Alexis Doublier]

Hi,

I have an application using a master window with two frame: top and
main.
I open a popup from main frame of my master window. Now i want to "open"
an new page in main frame from the popup when i click on a button. 

Can i change the source propertie of the main frame from my popup? if
yes how?
I think i must use something like that:
window.main.source="mycode.html"

Do you have an idear ?

Thanks

Alexis