Specifies the command key that is used in controlling DECwindows
   test sessions. The default command key is F9.

   The command key must be in the DECwindows Latin-1 KEYSYM
   encodings. Display the file DECW$INCLUDE:KEYSYMDEF.H with the DCL
   TYPE command to view the list of the Latin-1 KEYSYM keys.

   For example, to use F7 as the command key, enter the following
   command:

     DTM> PLAY test-name/DECWINDOWS/KEYSYM=F7