[Lizard]

The more I ponder it, the less I like my first batch of advice.
Either do the milestone thing, or........
The other approach would be to set end constraints on your tasks. That field is also in the inspector. Leave start dates and scheduling alone. Set your durations and your end constraints. Tasks will have early start and end dates until you set up all your dependencies, set up resource assignments, and apply leveling. But then, unless your schedule is well-padded (which one could argue it should be.......) your tasks will slide over toward their constraints.