Urgent: Help Needed

[dude23]

Hi

I do not know if this has been answered before but I am working on a critical project and need help.

I have customer data with channel (online etc ) in one column and the customer id in next column for two years. What I want is a formula to calculate unique customers in first year who repeated in second year for a particular channel.
Year 1
Channel Customer id Date
Online 1 ----
Walk In 2
Online 3
Online 4
Online 5
Online 3
Online 2

Year 2
Channel Customer id Date
Online 10 ----
Walk In 9
Online 1
Online 2
Online 2
Online 3
Online 3

The result should provide me with count of unique customer id which are repeated in year for a particular channel (say online).

 

[Peter_SSs]

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