Marchie

Ignoring the non-excel recommendations since this is a learning exercise: Although you have obviously done a lot of work to get this workbook the way it is, I think that you could improve the workbook by taking a different approach.

Personally I would recommend you doing all your data entry into a single worksheet and then use Pivot Tables to break out each month's data. If you do a search for a Pivot table tutorials you will get an idea of why this would be a good approach. For instance, have a look at https://www.youtube.com/watch?v=Vx-Fuw46VbY

Tutorials will no doubt show you how to display data by the month and filter based on various parameters.