So you can try to use TabTip.exe (Tablet Text Input Panel)
However I never saw how to request the numeric keyboard vs. the qwerty one
Like wise, you could use OSK.exe (On Screen Keyboard)
but it’s numeric keyboard is (IMO) fugly
IMO the best move is to write your own keyboard,
and make use of the APIs MapVirtualKey and Keybd_event
or PostMessage with a WM_Char
or if it’s all Clarion, maybe just use PressKey(…)