Improve performance of VBA macro

Hi,

What can I do to improve the performance of the attached macro?

The different sections of the code ('LOOP THROUGH SUBJECTS FOR SCREENING TEST CASE', 'LOOP THROUGH SUBJECTS FOR C1D1 TEST CASE', 'LOOP THROUGH SUBJECTS FOR C1D8 TEST CASE', 'LOOP THROUGH SUBJECTS FOR C2D1 TEST CASE' and 'LOOP THROUGH SUBJECTS FOR END OF TREATMENT TEST CASE') are all a little different in nature. So it's not possible to combine them in one loop.

Thank you for your help! Both the code of the macro, and the spreadsheet on which I'm running the macro, are attached.