As far as I can understand, you want to automate installation process. But many installers already have an ability to enter, store installation options in external file (.ins, .inf, .ini) and use it later (Administrative setup, Customization wizard etc.)
If it's not available, then you can:
1. Get an installer's window handle by caption using FindWindow() function.
2. Call SetForegroundWindow() to redirect keyboard input to window.
3. Place keystrokes into input stream using SendInput() or keybd_event() functions.

>Hi!, i have an little C++ App, i want add Keystroke for sending to another application, because i start an Installer, and i want sending a keystroke for the button Next, i see an article about that in VFP , but how i can do for do that? is possible?