Without delving into the code to fully understand the process... It would require using the OOB messaging process to pass the calendar entry data from the player to the GM (the GM will need to create the calendar entry on behalf of the player as the player doesn't have full access to the calendar portion of the database), then keeping the access correct to allow players to view the records. The problem would come with assigning ownership of a player calendar entry - what if 2 players want to add an entry on the same day? Do you end up with an entry for each player? What if they player wants to share their entry with the other players? This could soon get very complex - which is more than likely the reason why it hasn't been done yet.

