Compare Excel Workbooks with reference column, update only differences

I am not sure if this is a Programming/VBA/Macro or Formulas & Functions

I would like to update a master file with changes from several different files.
All data from all files is also in the master. However the Master report has all department information and the department report only has the information for that specific department.

I only want to update the changes from these files to the Master. Also, The Master will be having changes made to it as well.

I have done my best to described the scenario on the attached document.