I want the command ON KEY LABEL must work only on that form where I wrote it.

The problem with OKL's is that they interrupt any code that may be running at the point in time that they are triggered. This is a ( as you have discovered ) a global solution to a local problem. A much better way to handle this would be to use code like this in the KeyPress() method of the form in which you require this functionality (make sure you set the form's KeyPreview property to .T. ):

LPARAMETERS nKeyCode, nShiftAltCtrl
IF nKeyCode = -7 && F8
  DO FORM OTPTPOS.SCX
  NODEFAULT
ENDIF