I need help with what function to use. I am trying to find year to date information when I am given 12 month trailing information. January will not always be in the same column so what I am trying to do is do a lookup of the current month in my data series and sum it back "X" number of months. I have each month labeled 1,2,3,4, etc above the actual month to help with the lookup function. So what I was thinking is say for june it would look up the number 6 and then sum that month plus the previous 5 months. Then for July it would use the number 7 to run the lookup then sum all 7 months.

I guess my question is after running the lookup what kind of function would I use to sum the lookup# and all columns to the left of the lookup. I hope that makes sense. thanks in advance for the help.