Task from Subtask Custom Field Equations - Same as "Column functions"

It would be very beneficial to have a custom field be an equation of it’s related subtask fields. This would function just as “Column functions” do.

For Example: If my custom field is “Time” and I have 4 subtasks with 1 hour each assigned to that field, the master task would automatically update with a “SUM” of 4 hours. (Average, Minimum, Maximum, and Count functions ideally available as well.)

The reason this is a problem is that the Column Functions in list view factor in the fields of both the master task and subtasks in the equation which isn’t useful because they pertain to the same information and skew the equation.

For Example: If the master tasks “Time” field is 8 and each of the four subtasks is 2 than the Column function shows the SUM as 16, when it should ideally still be 8.