Switching Active Application

I am launching another Windows Application, but I only want to do this
if the application is not already running.

How can I check to see if another application is running ?

If the application is already running, I want to make it the active
application by switching to it like Alt Tab. I have achieved this in
the past with Microsoft Word using DDE, but in this case the other
application does not support DDE links.

How can I give another Application Focus ?


Chris Millard