SET (GLOBAL_SELECT_GRAB)

  Specifies the program or learn sequence TPU should execute whenever it
  automatically grabs ownership of the PRIMARY selection.

  Syntax

     SET (GLOBAL_SELECT_GRAB, SCREEN [, {program_source | NONE}])

  Parameters

     SCREEN               A keyword used for compatibility with future
                          versions of TPU.

     program_source       A string, buffer, range, learn sequence, or
                          program specifying the grab procedure.  If you do
                          not specify this parameter, TPU deletes the
                          current global selection grab routine; thereafter,
                          your application is not informed when TPU grabs
                          the PRIMARY global selection.

     NONE                 A keyword instructing TPU to delete the current
                          global selection grab routine.