Alternate BOM

Dear all,

How to use Alternate BOM ? How to give priority for the stocks availability of semifinshed material for finished material mentioned in BOM.

e.g. finished material - RA0100GR000 - Local requirement

For this we use Blanks ( SEmifinished ) --- DA0100GRL00 (Local),

DA0100GRE00 (EXPORT),

We have made Alternate BOM for RA0100GR000.

How to decide Priority for Blanks availabilty for the above material ?

We use first Local to local. But if it is not available in stock then we use Export blanks.

How to map this ?

Thanks.