milestone dependencies

It would be exceptionally useful to be able to assign dependencies on milestone/tasks. For example, if within a project I have three milestones for creating three ads for publication, but each ad also requires the logo to be finished by the graphic designer (a separate milestone), it would be useful to have the start dates of the later items dependent on another prerequisite component.

That way, not only would I not have to enter the logo creation as a separate task for each of the three milestones, but I wouldn't have to track and complete it three times once it is done. And if I'm late on the logo, it also knows I may be late or need to shorten my ad creation time if I have a deadline.