Posting Key determined in accounting docs.

Hi Experts,

My question is related to the following forum -

http://scn.sap.com/thread/1989714

Question is how to let Posting Key determined automatically in different Accounting docs., e.g.

1) After Posting GI using VL02N, Accounting doc. is under the Mat. doc.

2) After releasing Sales Invoice using VF02.

3) After Posting GR using MIGO, Accounting doc. is under the Mat. doc.

4) After Posting LIV using MIRO.

5) After Posting GL A/C items using FB50.

6) After Posting Vendor Invoice using FB60.

7) After Posting Customer Invoice using FB70.

Many Thanks,

KH Fong