Extrapolate/Fill or something?

Hi thanks in advance for any help.

Background:
I am building a project management dashboard with the aim of this piece to accurately show the booked costs and planned costs of current projects. There are two tables a booking table and a planning table and both of these tables work in a similar way with a month, project number, number of hours and a worker ID.

My issue:
The cost table has Worker ID, valid from and cost. The valid from is a period date in the format YYYY0MM - all of the tables use this, I have steps to convert it to a normal date everywhere.
I think I can do a merge to find the costs in the bookings and planning tables but I am not sure how to dynamically expand the costs table out and fill for each month/period to create something that can be merged.
Nice to have: as the projects are opened and the current projects change, the table as a minimum dynamically grows forwards in time based on the project planned furthest into the future.

Example of the cost table