Managing External Dependencies

I have a group of external dependencies, each of which blocks one or more of my project’s tasks, and I want to figure out need-by dates for them automatically. Does anyone have any advice in solving this?

In its simplest form, task A and task B require external dependency C in order to begin. I want to figure out automatically which date C needs to be delivered in order not to delay A and B. In my actual project, there are quite a few of these external dependencies, and some block half a dozen or more tasks. Doing this manually is a real pain, and would need to be repeated every time the schedule changes.

FYI, I tried this by creating a bunch of milestones, one for each dependency, and then scheduling them as ALAP. This had bizarre results… They appear to be scheduled completely arbitrarily. For example, one external dependency that blocks a task that’s scheduled for mid-May was set to start in mid-March. In fact, none of these external dependencies were set to start correctly. So I’m guessing that ALAP means something different than what I imagine it to mean.


With Task A selected, add your dependency as a Dependent using the inspector. Then edit that dependency and set it to be Start-Start. It will now ‘follow’ the start of Task A, such as when it’s pushed out by my task 2.1 running late.

OmniPlan example.oplx (16.4 KB)