MFC MDI : how i can handle when the program switch from a child window to another?

I have a MDI application and i need to do an action when the user (or the program) change from a child window to another.

I tried both with WM_ACTIVATE both on the View and the child frame wh开发者_如何学编程o own it but with no avail.

Those child are created from CMultiDocTemplate.

Thanks

Try WM_MDIACTIVATE instead.