Window focus vs. raising

I am fairly new to Gnome. One feature that I have been unable to find is
 how to raise one window on the desktop but leave keyboard focus with
another. In the documentation all I find talks about 'selecting' a
window which then implies both giving focus and raising the window.

Is there any way to make a distinction ?
(I have recently asked this question on the general list but got no
reply. Hope to do better here).

Appreciate any comments
Enno Fennema