Alternative BOM in Subcntracting

Dear All,

I have 2 BOM for one material which is subcontrating material.

System always selects 1st BOM bydefault. There is any option to select BOM so that we can select as per our requirement in PR/PO.

Always user has to change the BOM manually and there are 20 odd components with slide difference.

If anyone has idea please let me know.

Thanks in advance