Hi,
I understood your requirement. Suppose B0 is your initial level and after B0 release then B1 should approve. You want a report which provide the details of PO pending for release by B0 level before comming to you.
1. Try report ME2N, click on dynamic selection symbol. If B0 is your initial level, then take Release indicator to right side and enter status as '0' i.e blocked for processing. Also, you can find via 'Release status' - X means initial release XX means final release.
2. You can fetch tHE report from table level also. Try with table EKKO and CDHDR.
Please have a look at this link if it is helpful to you.
http://www.****************/Tutorials/Workflow/POReleaseStrategy/Details.htm
Regards,
Priti.