I'm looking for a javascript which allows the following:

I have a button, when I click on it I want the browser to open an extra window (300 by 300). I want users to preform an action on this window, before they can continue working in the main window.

Does anyone know what javascript I need...?

I have the following:

<input type='button' name='Button' value='Edit' onClick="window.open('edit.php?subcatid=$subcatid','','width=350,height=200,target=child');">

This does open a window, but I can still click in the main window...