testpid: PROCEDURE
PARSE ARG pid
LIBRARY rxcmd
command('PSLIST.EXE','Output',,'HIDE') 
DO i=1 TO output.0 
   IF WORD(output.i,2)=pid THEN RETURN 1
END
RETURN 0

/* Register FindWindowA() */
FUNCDEF('FindWindowA', 'void, str, str', 'user32', , 'o 0')

/* Call FindWindowA() to locate our Target.rex's window. All REXX
 * GUI windows have a class name of "rexxgui". Assume that the
 * titlebar of Target.rex's window is "My Window".
 */
targetwindow = findwindowa('rexxgui', 'My Window')

/* Is the window open? */
IF targetwindow \== '' THEN DO

  /* You found the window. Here you can do something like
   * call GuiSendMsg to send it a custom event with an
   * arbitrary ID number and data values that tell it to
   * do something.
   */
  guisendmsg(targetwindow, 40000, /* Pass some numeric value here,
     if desired */)

END

DO FOREVER
	guigetmsg(,mysignalnumber)
	IF EXISTS('GuiObject') == 0 THEN DO
		IF EXISTS('GuiSignal') THEN DO
		END
	END
...

guisendmsg(targetwindow, 40000, mysignalnumber)

guisendmsg(targetwindow, 40000)

/* ===================== WM_EXTRA ========================
 * This handles all events for our window which REXX
 * GUI doesn't know about (ie, custom events).
 */

wm_extra:

  /* Figure out what to do based on the event number */
  SELECT ARG(3)

    /* Is it our custom event number 40000? */
    WHEN 40000 THEN DO

      /* It's the 40000 event we GuiSendMsg()'ed above */
      SAY "Received event 40000"

    END

    OTHERWISE

  END

  RETURN ""

guisendmsg(targetwindow, 40000, 1)

wm_extra:
  SELECT ARG(3)
    WHEN 40000 THEN DO
      SAY "Received event 40000 with ARG(1) =" ARG(1) /* ARG(1) will show as "1" */
    END
    OTHERWISE
  END
  RETURN ""

guisendmsg(targetwindow, 40000, 1, -1)

wm_extra:
  SELECT ARG(3)
    WHEN 40000 THEN DO
      SAY "Received event 40000 with ARG(1) =" ARG(1) "and ARG(2) =" ARG(2)
    END
    OTHERWISE
  END
  RETURN ""

guisendmsg(targetwindow, 40000, , -1)

guisendmsg(targetwindow, 40001, 100)

wm_extra:
  SELECT ARG(3)
    WHEN 40000 THEN DO
      SAY "Received event 40000 with ARG(1) =" ARG(1) "and ARG(2) =" ARG(2)
    END
    WHEN 40001 THEN DO
      SAY "Received event 40001 with ARG(1) =" ARG(1) "and ARG(2) =" ARG(2)
    END
    OTHERWISE
  END
  RETURN ""

wm_extra:
  SELECT ARG(3)
    WHEN 40000 THEN DO
    END
    WHEN 40001 THEN DO
      RETURN 1000
    END
    OTHERWISE
  END
  RETURN ""

guisendmsg(targetwindow, 40001, 100)
SAY "Return value from event 40001 =" guisignal

guisendmsg(notepadwindow, "CLOSE")

STREAM("C:\MyFilename", "C", "OPEN WRITE REPLACE")
VALUEOUT("C:\MyFilename", guiwindow, , 4)
STREAM("C:\MyFilename", "C", "CLOSE")

STREAM("C:\MyFilename", "C", "OPEN READ")
targetwindow = VALUEIN("C:\MyFilename", , 4)
STREAM("C:\MyFilename", "C", "CLOSE")

LIBRARY rexxgui, rxclip

/* Get the server script's window handle. The server
 * script should have stored it on the clipboard using a
 * custom format named "WindowHandle". Let's store it in
 * our "ServerWindowHandle" variable.
 */
FORMAT = clipnewformat("WindowHandle")
IF clipavailable(format) THEN DO
   clipget("ServerWindowHandle", format)

   /* Send the server window a custom event of 50000, with
    * one additional arg of our own window handle, which
    * we assume is in our GuiWindow variable.
    */
   guisendmsg(serverwindowhandle, 50000, guiwindow)
END
ELSE guisay("Server script isn't running")

LIBRARY rexxgui, rxclip

guicreatewindow('NORMAL')

/* Let's create our own custom clipboard format with a name
 * of "WindowHandle". Then we'll store our window's handle
 * on the clipboard so some other script can grab it.
 */
FORMAT = clipnewformat("WindowHandle")
clipset("GuiWindow", format)

/* No one has sent us any window handles yet */
handlecount = 0

again:
DO FOREVER
   guigetmsg()
   CATCH SYNTAX
      CONDITION()
      SIGNAL again
   CATCH HALT
   FINALLY
      guidestroywindow()

      /* Remove our window handle from the clipboard */
      clipclear()
END
RETURN

wm_extra:
   SELECT ARG(3)

      /* Is it our custom event number 50000? */
      WHEN 50000 THEN DO

         /* Someone GuiSendMsg()'ed us its window handle.
          * Let's store/add it to our list of window
          * handles we have. We use the Child. stem
          * variable to hold these.
          */
        handlecount = handlecount + 1
	child.handlecount = ARG(1)

        /* Now we can send that other script some custom
         * event too.
         */
        guisendmsg(child.handlecount, 40000, 1, -1)

      END

      OTHERWISE

   END

   RETURN ""

DO i = 1 TO handlecount
   guisendmsg(child.i "POST", 40000, 1, -1)
END

   /* Send the server window a custom event of 50000, with
    * one additional arg of our own window handle, which
    * we assume is in our GuiWindow variable, and an additional
    * arg of "__ME" as a unique identifier.
    */
   guisendmsg(serverwindowhandle, 50000, guiwindow, "__ME")

wm_extra:
   SELECT ARG(3)
      WHEN 50000 THEN DO
        handlecount = handlecount + 1
        /* Store both the window handle, and ID string */
	child.handlecount = ARG(1)
	id.handlecount = ARG(2)
      END
      OTHERWISE
   END
   RETURN ""

guisendmsg(serverwindowhandle, 40000, 1, "__ME")

wm_extra:
   SELECT ARG(3)
      WHEN 40000 THEN DO
        guisay("Received event 40000 from" ARG(2) || ". ARG(1) =" ARG(1))
      END
      OTHERWISE
   END
   RETURN ""

guisendmsg(serverwindowhandle, 50000, guiwindow, "__ME")

clipset("MyVar.", dictin)  /* trigger Clip event and process at Server */
...
guisendmsg(target, event, p0,p1) /* see when clip event is completed */

guisendmsg(target, 40000, C2D("__ME"))

wm_extra:
   SELECT ARG(3)
      WHEN 40000 THEN DO
        id = D2C(ARG(1))
        guisay("id string =" id)
      END
      OTHERWISE
   END
   RETURN ""

guisendmsg(target "POST", 40000, C2D("__ME"))
guisendmsg(target "POST", 50000, C2D("__ME"))

guigetmsg()
guigetmsg()