How to use GotFocus event / LostFocus event in wpf ?

Hi guise,

I have created wpfwcf  Chatting  program  and i want to use  GotFocus Event And GotLost Event  because  if i am working on another form or application and user send me some message  than i want to focus on it. how to use it?

Please Let me know .

---

Regards: Balram