Thanks! That is a Lag description I wouldn't find anywhere else! As asked for above, here is a data set that is typical for my input table. Three levels of variables/fields (DateMY is in mmyys7.). The lag sums need to be calculated for each SN-Name combination, increasing by date, SO after 101-Name1 lag sums are complete, the lag1-6 queue needs to go back to 0 for lag(n). Then back to zero after 101-Name2, 201-Name3, etc. The data would be sorted as shown. SN Name DateMY Count (WANT-Lag cum_sum) 101 Name1 11/2017 12 12 101 Name1 12/2017 4 16 101 Name1 02/2018 3 19 101 Name1 04/2018 3 22 101 Name1 05/2018 7 29 101 Name1 07/2018 8 37 101 Name2 03/2018 1 1 101 Name2 04/2018 1 2 201 Name3 03/2018 5 5 201 Name3 05/2018 6 11 202 Name1 01/2018 1 1 202 Name1 03/2018 2 3 202 Name1 05/2018 7 10 202 Name2 02/2018 2 2 202 Name2 03/2018 0 2 202 Name2 05/2018 2 4
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