Hi, I want to creat a conditional sum in CR10.

I have a column of budget amounts ({glamts.budget1}) which is being compared to a more detailed actual (budget is a single entry per month, and actuals contains many entries per month).  Placing them side by side with a detailed view of the many line items, the budget data is duplicated for every instance in the actuals column. 

I can suppress the duplicates of budget data so that only a single instance is displayed, but when I sum that column, it still sums all the instances (even those suppressed). 

I also have a column of period numbers (periods 1-12 representing months).  I would like to write a formula that only sums the budget instance that corresponds to the first instance of each new month in the period column.

Can someone give me ideas of what that formula might look like? Or, would I be better off with a different approach?

Thanks,

Paul