vba event - change within a sheet triggered by reference

Hello all,

I'm afraid, being a non native speaker I didn't find a suitable title and I might not be able to explain my goal on the first try.

I have several sheets in my workbook (the example has only two which is enough to show my problem, I hope).
When I change the year in D10 on the first sheet, it will change the values in column B and the year is referenced on all following sheets which are designated as month.
Cells are colored when it's a working day and non colored during holidays, vacation and weekends.
As the year is only referenced on every other month from the first sheet I used the "calculate" event to trigger my code.
So far so good.

Now to the one thing I can't solve myself right now: I only want to trigger the process on all sheets after the first one, when the D10 cell is changed and no other. But I can't figure out how to do that.
Maybe a different approach would be better, so I'm open to suggestions.

Sadly my vba knowledge is quit limited, so the code is rather crude. I have search for possible solutions before posting here, but I've either not found a fitting solution or was unable to adapt my code.

Best,
Edward