Hi Leondi,
You may use SAP standard scenario Setting of head office and Branch accounts. Just go through the mentioned link ,which will help to you.
http://help.sap.com/saphelp_470/helpdata/en/01/a9b317455711d182b40000e829fbfe/content.htm
There is one more key called Corporate group under control which will help grouping the customer under single group.
http://help.sap.com/saphelp_45b/helpdata/en/01/a9b23a455711d182b40000e829fbfe/content.htm
Both are standard ,you may use.
Regards
Mani