Getting matching counts in different months

[#1]

I have set of data for different months. I would like to see matching records for next month from previous months.

Jan, Feb, March, April

I want to see what is matching in feb for january counts, what is matching march for feb conunts

basically having inner join between different months

say january has 100 counts and february has 120 counts but february has matching count of 80. I would like to diplay 80 in a different column.

[#2]

Possible to attach a dummy file with some data?

[#3]

Its like month 1 will have 2,429000 records but month 2 will have 2 million matching records probably out of 3 million  so we need to calculate matching records in next month numbers .

[#4]

Finally got it working. I created a flag called Flag which will compare data with previous month and see how many Item# match and display the sum in it.

Check out the attached and see if it helps.

Thanks

AJ