You can use standard reports to get the opening/closing stock datewise: MB5B, period wise: (e.g.) MC.A - from MC.A you can also get avarage stock (please click on the field, push F1 - you will get the description how it is calculated) > table S039 is used for MC.A.
U can get the opening and closing stock as per material using TC:MB5B
but if ur looking for a table or a SAP report dat directly shows u each material corresponding to its opening and closing stock dep on d date , i don think a direct solution exists.
however wid a lil calculation u can create a report dat serves d purpose .
if u do need a sample do revert back and il b glad to give u d code!