Column change where pull values from according to the month

Hi All,

Please let me know if the below are possible and how:

I have a workbook with multiple sheets named "SUMMARY" (Master sheet), "MAR", "APR", "MAY", "JUN" etc. Once every month new data is copied into the current month sheet.(Column A2:A2000, B2:B2000)

1. I want column "A" in worksheet "SUMMARY" to change the location where it get the values according to the current month. For example in MAY I need "SUMMARY" sheet Column "A" to have the updated numbers from "MAY" sheet and next month in Jun from column "A" in "JUN" worksheet and so on.

2. The values are customers account numbers. If new values (customer accounts) are found one month (but were not there previous month) to display in cell "B" in worksheet "SUMMARY" the word "NEW" and other way around if same value one month is not present anymore to display "NO DATA". Each month are some new and some customers that left.

I use Excel 2010. Thanks in advance