Hi,
First let me correct your entries in cash sales process:
Cash A/C - Debited
Revenue - Credited.
Now, coming to COGS its very interesting scenario. Even i am very curious to learn this. After reading your question, i did bit of search in SCN found similar type of questions. Some are suggesting CO-PA as one of the options.
Please check below threads may help you.
http://help.sap.com/saphelp_46c/helpdata/en/7a/4c3a934a0111d1894c0000e829fbbd/content.htm
http://scn.sap.com/thread/1811492
http://scn.sap.com/thread/1305469
Regards, Sai Krishna.