Applications stealing focus

Is there any way in Snow Leopard to disable applications stealing focus?

For example, last night I used the Print… Preview command to check a 100pg PDF. While the PDF was being made, I was doing work in Word. A couple of minutes later Preview started up and stole the focus, and I lost a couple of sentences I was typing because I wasn't in Word any more.

I've seen plenty of posts with people describing this problem, but no solutions - except a way to stop swapping between Spaces when it happens.

I don't use Spaces - I just want a way to stop applications unwantingly demanding my attention. And I'm not looking for a way to quickly swap back to the original application - I don't want it happening in the first place.

Thanks.

- Richard