Intersecting parts in an assembly

Hi

I've got an assembly with 2 intersecting parts.  I want to leave B unchanged, but create a cut (recess) in A where it intersects with B.

This is a simplified example - the real assembly I'm working on is much more complicated so creating the recess manually is a lot of work, and I need it to change as the shape of B changes.

Is this possible?  I know there's an Intersect feature in SW 2013 onwards, but I'm using 2012.

Many thanks

SolidworksParts And Features