Display Submenu
Displays a submenu.
Example--display submenu statement:
The following example illustrates use of the display submenu to define a submenu that is displayed when the user selects the menu item option1:
## activate menuitem "option 1"
## {
## display submenu
## activate menuitem "option 1a"
## {
## program code
## }
## activate menuitem "quit"
## {
## enddisplay
## }
## }