Hi Praveen
i think your requirement can be addresed through BOM transfer t code CN33.
you have to maintain the reference points at activity and you create wbs bom using t code CS71
you have to maintain reference point at the subcomponents of BOM.
once you run t code CN33 the bom items and activity have same reference points gat attached,
so when ever there is revised BOM ,attach the reference point to revised item, thus run the cn33 t code the BOM gets updated in Project
hope this Answers your question