I desperately need some help with varying a range in a function. I'm trying
to make some of my reports more automated, and I would like to be able to
fill out one reference cell with the current month and have the formulas now
include any new data into their calculations. I can't simply use yearly
totals as I often want to compare the same time period last year to the
current YTD.

For example, if January's data is in cell C4 and I want to add the current
YTD I'd like to be able to write a formula that is SUM(C4:C("current month")).