Like the Help Topics call, it is common to call the Index function of the Help Viewer from the Help menu. The following pseudocode calls the Help Viewer with the Index tab on top:

ON CHOOSE OF Button_Search IN FRAME frame_1 DO:
   SYSTEM-HELP myhelp.chm KEY "".
END.

The following figure shows the Help Viewer for the Procedure Editor help file with the Index tab on top.

Figure 1. Help Viewer with Index tab on top