I'm using a sumif formula which is working to calculate a sum of data on a
sheet but it is calculating the sum for the entire sheet which goes back five
years. I only want the sum for the previous 6 months which will automatically
update itself with the answer. the formula I have is
=SUMIF(Type,"P28R",Logbook!O:O)
where "type" is a column heading and P28R is a criteria under the type
column and logbook is the name of the entire sheet in excel.

Thanks for any help!!!