Migrate a "3-D" Spread sheet to an Access Database

I have a working project management Microsoft Access database that I continue to develop, adding new processes that help  consolidate all projec t functions into one tool where I can combine data to generate composite reports  

With each new process I learn new techniques

The latest element that I am trying to add is mimicked in the attached spread sheet - the challenge I am faced with is that each contract has a different menu of "Billing Code / Activities" (Column b-f) and then there are monthly billings that occur for the life of the project (col g-o, col p-x, ...)

The typical working spreadsheet has a number of other tabs - but this is the "core data" for each contract.

Currently I manually build the spreadsheet for each project and then manually migrate data from the spreadsheet to my database each month.

Does any body have an example of a "3-d" table structure I could use as a starting point?
PAY-Application-Review-Sample.xlsm