Updating Progress

Question

When you specify the percentage of completion for a task, Project calculates the actual duration and remaining duration according to the formulas Actual Duration = Duration * Percent Complete and Remaining
Duration = Duration - Actual Duration. 
I would like Project to calculate the actual duration and remaining duration differently. 
I would like the Percent Complete to be the difference between the Data Date and Actual start. 
Then I would like the remaining duration to be shown as the percent left to complete based on the new actual duration. 
Basically, I want to type in an actual start date and a completion percentage and have Project calculate.
Example:
What Project Does:
Original Duration: 5 days
Actual Start 3/11/15
Data Date: 3/16/15
Percent Complete: 20%
Actual Duration: 1 day
Remaining Duration: 4 days
What I want to happen:
Original Duration: 5 days
Actual Start: 3/11/15
Data Date: 3/16/15
Percent Complete: 20%
Actual Duration: 4 days
Remaining Duration: 
20 days
Project will only calculate this to have an Actual Duration of 1 day and a Remaining Duration of 4 days. 
Is there any way around that without having to manually calculate it?

Answer 1

djburke,
The first thing you should understand is that percent complete is not a good indicator of task progress. Why? Because it is simply based on passage of time (i.e. duration). A much better indicator of progress is the amount of work completed since work is
what gets things done.
Given that, what exactly is your "data date"? Is that the Status Date as defined by Project?
With respect to your question, you can certainly create custom fields to do pretty much whatever calculation you want, but those fields will not interact with the standard built-in fields. In other words, you can create a set of custom durations fields but
they will have no impact on the Duration, Actual Duration and Remaining Duration fields.
On a specific question on your example. How can a task with a 5 day duration suddenly have 20 days of remaining duration, four times the original duration? Are you perhaps thinking that the "original duration" will stay at 5 days when you manipulate
the actual and remaining duration? If so, you may be unaware of baseline fields. The only, and correct, way to capture the original plan is to set a baseline. That will preserve that original 5 days of duration, but the Duration field will be updated to reflect
what is really happening as the plan unfolds.
Just some thoughts, but the bottom line is, what is your end goal?
John