How to Get number of Day’s interval by Looping Through spreadsheet

I have an excel spreadsheet containing 140K rows. The requirement is to find “number of Call days between calls on the same Client for the same product”. I have created the Key( Column E) by concatenate Column B and C. The expected output result is put into Column F. For example value 8 under column F was derived by =NETWORKDAYS(D4,D5) which is 4/6/2015,4/15/2015.

I am looking for a VBA code to go through the entire ~140K file and write the # of Days Interval into Column F.


Rep(Column A) Client Name(Column B) Product(Column C) Call Date(Column D) Key(Client+Product) Column E # of Day's Interval (F) - Expected Output Value
Rep 1 Client 1 Product 1 5/20/2015 Client 1-Product 1 0
Rep 2 Client 2 Product 2 3/31/2015 Client 2-Product 2 0
Rep 3 Client 3 Product 1 4/6/2015 Client 3-Product 1 0
Rep 3 Client 3 Product 1 4/15/2015 Client 3-Product 1 8
Rep 4 Client 3 Product 1 4/15/2015 Client 3-Product 1 0
Rep 3 Client 3 Product 1 4/22/2015 Client 3-Product 1 6
Rep 4 Client 3 Product 1 4/30/2015 Client 3-Product 1 7
Rep 3 Client 3 Product 1 5/13/2015 Client 3-Product 1 10
Rep 4 Client 3 Product 1 5/13/2015 Client 3-Product 1 0
Rep 3 Client 3 Product 1 6/3/2015 Client 3-Product 1 16
Rep 4 Client 3 Product 1 6/11/2015 Client 3-Product 1 7
Rep 3 Client 3 Product 1 6/19/2015 Client 3-Product 1 7
Rep 5 Client 4 Product 1 6/3/2015 Client 4-Product 1 0
Rep 5 Client 4 Product 1 6/19/2015 Client 4-Product 1 13
Rep 5 Client 4 Product 2 4/13/2015 Client 4-Product 2 0
Rep 5 Client 4 Product 2 5/29/2015 Client 4-Product 2 35
Rep 5 Client 4 Product 3 4/24/2015 Client 4-Product 3 0
Rep 5 Client 4 Product 4 6/15/2015 Client 4-Product 4 0
Rep 6 Client 5 Product 5 5/18/2015 Client 5-Product 5 0

You should post an actual workbook.

With a sample workbook. Make sure there is just enough data to demonstrate your need. Include a BEFORE sheet and an AFTER sheet in the workbook if needed to show the process you're trying to complete or automate. Make sure your desired results are shown, mock them up manually if necessary.
Remember to desensitize the data.

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