I want to show an ongoing "support" task in MS Project, where the start date is driven by one milestone (test environment available), and the end date is set by another milestone (testing complete). I do not want to enter a duration or an amount of effort into the plan, as these will vary according to whether my dates vary as the plan evolves. Instead, I would like to have these figures calculated within the system and recalculated automatically if the plan moves.
I feel as though I am missing something obvious, but can't work out what it is. Is this possible, and if so, how do I do it? It's not quite the same problem as in < Calculated duration in MS project task? >, but it does seem fairly similar.