I have a cross table in Business Objects which displays customer number in the rows, financial month in the columns and the values are items purchased in each financial month. As seen here in the Excel mock-up
What I want to do is find every such row (customer) where there is at least a three month gap between purchases and flag that customer. With reference to the picture above, customers 10001, 10002 and 10005 would have a flag based on the data in this table. My actual data covers several financial years and hundreds of customers. It doesn't necessarily have to be in this layout; a standard vertical table would be fine if I could then have a formula that would return the length of the maximum days between purchase dates across the whole timeline per customer.
I have tried making use of Previous(), ForEach(), DaysBetween(), In etc. in different combinations but with no success. Can anybody provide some guidance on this please?