RE: how to make duplicate items in purchase order

I want to add a field in this report shows Number Duplicate ItemLookupcode  In purchase order

For example

Item LookUp Code

BI0-IP0002

BI0-IP0003

BI0-IP0004

BI0-1P0004

BI0-IP0005

BI0-1P0005

BI0-IP0006

BI0-1P0006

BI0-IP0007

BI0-IP0007

BI0-IP0007

=====   item  Duplicate  

Item LookUp Code item   Duplicate  

BI0-IP0002 1

BI0-IP0003 1

BI0-IP0004 2

BI0-1P0004 2

BI0-IP0005 2

BI0-1P0005 2

BI0-IP0006 2

BI0-1P0006 2

BI0-IP0007 3

BI0-IP0007 3

BI0-IP0007 3