Thermal Expansion 3: Managing cyclic assembler inventories?

Ok, so cyclic assemblers are brilliant for simple crafting, but how in the world do I stop their inventories from getting clogged when I need more than one item for a recipe?

Say I want to make sandy blocks from railcraft. I would have to send it clay bricks and sand, but how do I stop the inventory filling up with one of them and blocking the other?

I'd really appreciate any help!