Is it possible to use a custom expression to set the tracking mode for tasks?

[BrookeSt1]

We are trying to create more accurate projected start and finish dates for tasks by using both the "Assume on Time" and "Predecessor" tracking modes within projects. Our users are not great about saying when they start tasks, so the "assume on time" mode is best for any task that can start. This assumes they will finish on time until the due date, then the projected finish date is one day out. But for tasks which are waiting for others to complete, the "Predecessor" mode seems best.

I'd like to set the tracking mode of any task using a custom formula, something along the lines of: IF the task can Start, Then Tracking mode = Assume on time, Else tracking mode = Predecessor. Does anyone know a way to apply a valueexpression to the tracking mode? Thanks for the help.