Ok. I don't think that there's a way to automatically do this, though I admit it would be a cool feature to have. Perhaps it can be done via a Zimlet, I don't really know.
One thing you can do "in the meantime" is, using ZCS7, you can create the appointments and choose the "Save" option to create them but not send out invites and then, manually, the day before you would open the appointment and then select "Send". Just a suggestion, I know it would help (a lot) if it was done for you, but still... |