You can set your Alt+Number macros to send messages. I forget the menu that changes it - but I assume it's Alt+M ??? Then you can set a macro to send those messages. My Alt+1 is set to @autoloot and Alt+2 is set to @main off
I remember doing the Juperos 2 door openy thingy quest on an old server where it was buggy, to get everybody into the elevator at once we all had to pre-click the way through and then click 'yes' at the same time. We used Alt+M for the party to say when they were ready and when to go =P