There is clearly a reason why you add data to one or other of the worksheets. Why not just add a column to store that reason, possibly using Data Validation? Then you just have the Combined worksheet with the ability to filter on any of the reasons, or, for that matter, any column or combination of columns. No complex merge process, no VBA, and no duplication of data ... which will, effectively, double the size of your workbook.

Regards, TMS