WH,
I guess when you performed your searches, before you posted this question (you did perform a search, right?) you overlooked the extensive coverage contained in SAP online help.
Creating Purchase Order Commitments - Commitments Management (CO) - SAP Library
Before posting other questions on SCN, do yourself a favor by checking out the following two URLs:
especially rule 3 under 'etiquette'; and
http://help.sap.com/search/sap_trex.jsp
Best Regards,
DB49