>>I have the window Handle now I need to bring that window application as the top application in windows.
>>
>I've searched for ShowWindow on that site.

Actually, SetForegroundWindow or BringWindowToTop may do the job, but not in all cases.

For Excel I use BringWindowToTop and then ShowWindow.

Unfortunately, I'm still having problems with the image of Excel still showing on the screen after I pressed Close button. I don't know how to solve it and clean the image immediatelly. Though I guess some API solution exists for this problem as well, I just need to find one.