User Exit for XD02 in Sales area data in Sales tab

Question

Hi Sap Gurus,
I have a problem . I need help .
The requirement is
In XD01 transaction , In Sales area data, In Sales tab i need to add a Check box which i already have added.This check box refers to KNVV table-Zflag
In VA01 transaction , In menu goto -> header -> Sales , In Additional data B .
I have another Check box.  This check box refers to Vbaktable-Zflag .
<b>I need the code and exact locations where to put this to get my issue resolved which is given below in Functional Description</b>.
Functional Description where you can understand better.
   Our custom logic will be initiated once the Sold-to Party (VBAK-KUNNR) is entered for any order type.  When the sold-to party is entered the user exit program will check table KNVV for the custom field ZFLAG that corresponds to the “Print Prices on Delivery Note” flag (hereafter referred to as the Pricing Flag) and populate the same setting of the flag into the ZFLAG that will be on the “Additional data B” tab on a sales order at the header.  The user can manually change VBAK-ZFLAG Pricing Flag setting to something different than what is populated for the customer master level.
If the user happens to change the sold-to party for any reason then the user exit program should take the following approach when populating the ZFLAG Pricing Flag in a sales order:
-     Recheck the ZFLAG Pricing Flag setting in the customer master for the sold-to party that the user has newly selected.
The user will still have the option to manually ZFLAG Pricing Flag on a sales order after the user exit program defaults it.

Answer 1

Transaction Code - XD02                     Change Customer (Centrally)
Exit Name           Description
SAPMF02D            User exits: Customer master data
No of Exits:          1
USER EXIT
http://www.sap-img.com/abap/a-short-tutorial-on-user-exits.htm
http://www.sapgenie.com/abap/code/abap26.htm
http://www.sap-img.com/abap/what-is-user-exits.htm
http://wiki.ittoolbox.com/index.php/HOWTO:Implement_a_screen_exit_to_a_standard_SAP_transaction
http://www.easymarketplace.de/userexit.php
http://www.sap-img.com/abap/a-short-tutorial-on-user-exits.htm
http://www.sappoint.com/abap/userexit.pdfUser-Exit
http://www.sap-img.com/ab038.htm
http://help.sap.com/saphelp_46c/helpdata/en/64/72369adc56d11195100060b03c6b76/frameset.htm
http://www.sap-img.com/abap/a-short-tutorial-on-user-exits.htm
http://www.sap-img.com/abap/what-is-user-exits.htm
http://expertanswercenter.techtarget.com/eac/knowledgebaseAnswer/0,295199,sid63_gci982756,00.html
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