Date and Name Table that grows

There are two tables, Date and Users.  I am trying to create a third table or virtual table, of Month Start Dates, and User Names for each month.  I can then add a column or measure of Phone calls, and meetings.  Everyone needs to make 80 calls, 60 meetings, I can do this part. Basicly this is a User monthly target table, that will measure actual data, calls and meeting from another source.

The challenge is building this new table for each User and each StartOf Month; expecially when a new User Name (we hire someone) is added is populated to the User Table.  The new employee/user automaticly gets added this (virual, M or DAX) table at each StartOfMonth Date table. It does not have to be smart enough, to read the employee start onward, have an HR table that will not "count" calls/meetings from prior periods.