Hi Andy,
Yes, that's absolutely possible, though a little trickier. You need to first know the object type of the form you're building (Task), the object type where the field you want to reference exists (Project), and the exact API name of the field on the other object. My very simple example below on a Task form would concatenate the Name of the Task itself, then go to the Project and get the Name field to concatenate that next.

In your example, let's say that the 'DE:IC - Channel' field were actually on your Project object, you would alter the formula to read as below.
- Before: {DE:Segment},"-",{DE:IC - Channel"}
- After: {DE:Segment},"-",{project}.{DE:IC - Channel"}
This can be used for more than one jump, going back to my original example and say I wanted to pull in the name of the Portfolio that the Task's Project lived in, I would do that as below. That can be a little tricker because you have to know the relating object as well, a Task doesn't have a Portfolio, that attribute belongs to the Project the Task is in.
