focus on window

Hi there,

I used some javascript to open a window (on request) which is how I wanted
it to be (size, toolbars,...). Now, how can I get the focus back on my
original window (after I chose some options that were brought back to this
original window) ? 

Same question when to go back to the pop up window (if it is not destroyed
the first time, I do not get the focus on it).

 many thanx.

Vince.