Sorry Arvin but I'm equally unclear what the 'day2 day1+2-day2' type calculation means.
I can't see how the examples such as '9 20+2-9=13' fit in with the previous supplied data.

I also don't have a clue why you would need to do this
...but that's less important than knowing what you actually want



Suggest you do the same as in post 1. Post the source data and the desired outcomes.