MRP x ECM valid date

Dear Gurus,

I have a scenario here that is the following:

We do have make to order and run MD50 to generate planned orders based on delivery date in manufacturing sales order.

We also have ECM implemented to control BOM modifications and dependecies ruels as weel.

Is it possible to run the MRP considering a date in the past on sales order manufacturing and get the BOM list valid on that time.

For example, we have a sales order with delivery date set to the past, lets say 04/2012.We have an ECM implemented on 05/2012 that modifies the BOM list. Is it possible to run the MRP and get exactly the bom list on 04/2012, before the aprove of the ECM on 05/2012?

Kind regards

Oliver F