Hosting processes and "Sleep"

Hi!
I'm trying to host some processes in my WPF window.
In order to do so, I used HwndHost and put it in a border.

The problem is that if the guest process "Sleep"s (with Thread.Sleep for example) - It puts my hosting process to sleep to.

I tried starting the guest process and then in another AppDomain  and then passing its "main window handle" to the appdomain which owns my window but it didn't help.

How can I solve this? How can I prevent my host process from sleeping when the guest process sleeps?

Thanks! :)