While the Domino Designer help files describe the @command([OpenCalendar];Username) as a very simple command that will open a users calendar there is an extra undocumented parameter that will instruct the notes client to open the users calendar in the proper calendar frameset.
@command([OpenCalendar];username;[UseFrameSet]) will open the calendar in the calendar frameset.
@command([OpenCalendar];username;[UseMailFrameSet]) will open the users inbox in the mail frameset.
So why is this undocumented? The ND6 mail template uses the undocumented commands as part of it’s functionality to open listed users calendars. Infact why keep things that are useful hidden in the product. Every version of the Notes client that has come out has always had something hidden, like the formula debugger in R5 and the extra admin panel options in R4.
What else is hidden in there that we don’t know about?