First level BOM in the multi-level scenario and efficient use of time basis code

Hi,

Please help me in the below two situations.

a) How to find items at the lowest level BOM in the multilevel scenario?  i.e list of all items whose BOM do not contain any further manufactured items as component.

b) The best and efficient way to use time basis code when there is lot of batch BOM in system as the variables used in the UDC/30 TB (time basis code) is exhausted with the use of all possible characters and symbols.

Regards,

Gaurav