Hello,
Please have a look to the documentation on help.sap.com for the retrofit functionality :
[http://help.sap.com/saphelp_sm70ehp1_sp23/helpdata/en/b6/6de59f9abc4d17a04ac6486c2e8b84/frameset.htm]
Alternatively you can check this blog for more technical details :
[http://www.sdn.sap.com/irj/scn/weblogs?blog=/pub/wlg/15616] [original link is broken] [original link is broken] [original link is broken];
Hope this helps.
BR
Stu00E9phane.
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