When the user selects "Using help" from the help pull-down menu, a WM_COMMAND is sent to the application's window procedure.

If the application has created its own "Using help" window, it responds by sending the HM_REPLACE_USING_HELP message with the help-window ID. If the application chooses to use the "Using help" window provided by IPF, it responds by sending the HM_DISPLAY_HELP with NULL in both parameters.

Current CUA guidelines recommend applications use "Using help"; however, IPF continues to support the "Help for help" window.