I'm trying to keep a running total by adding the difference. Here's an example...in cell A1 I enter my week ending sales numbers, let's say $1500 and I want to keep a running total in cell D1 of my Year to Date Sales numbers so now, D1 should show $1500. Next week I will enter $3200 in cell A1 and I want D1 to show a YTD number of $3200. That part I think is pretty easy ( I could simply use D1=A1 but...the part where I'm having problems is that staring in July (or whatever the next month is) I will be tracking new weekly numbers so I want cell D1 to keep adding the difference, if that makes sense? So after the first week in July I enter $1000, now D1 should say $4200 and then at the end of week 2 in July, I enter $2500 (which is my new MTD total) so I want D1 to now say $5700.

I hope this makes sense because I'm getting lost just typing this