Sheduling externals

Dear folks,

i've got a problem modelling in external appointments in Planner.

Say i need a carpenter to help me with a specific task in building the
proverbial doghouse. I can model that task fine and have the dependencies set
all clear. So far, no problems.

But now say he can only come by next tuesday at 15:00 for one hour. It would
be nice to model that too but i can only specify the day he comes by in
Planner, not the time! The only option for now is to create a dummy task with
fixed duration on the date and make de carpenter job dependent on that. That
shouldn't be nessisary!

Can this already be done? Or is it a GUI issue?

With regards,
Reinoud