Master Planning for materials only

Hi,

We'd like to run the planning for material level. We have firmed production plan and want to explode to sub-assembly and materials as is (do not take on hand/transactions into consideration). But on material level we want to include on hand/open transactions.

e.g. Plan X as is, explode Z as is (do not include on hand/transactions),  calculate requirements for Y, Z1 and Z2 (include on hand/transactions).

What is the best way to implement this? I have tried several ways (different master plan versions, firmed planned orders and rerun MRP, run MP once go change parameters and select only materials and run again,...) but it does not look OK.

Any suggestions/experiences will be appreciated.

Thanks.