How to source the value of a Project Task Estimated Cost to a Project Custom field?

I've found multiple SuiteAnswers and Community suggestions for this question, but not exactly what I am trying to do.

In a Project record, there is a field named ACTUAL WORK TIME ENTERED with a FieldID = actualtime. It pulls all the labor hours for all the Project Tasks into (in our case) a field in the Project Overview category of the Project record. I am trying to do something similar.

In each of our Projects, we have created a Parent Task with a name that starts with the words "BILLING RECORDS". There is only one such BILLING RECORDS Project Parent Task in each project. This Parent Project Task summarizes multiple Child Project Tasks below it. The particular total field I need to source from the BILLING RECORDS parent task is named ESTIMATED COST. My goal is to place that total amount in a new field under the ACTUAL WORK TIME ENTERED field that I reference in the paragraph above.