Load balancing a couple of CIFS shares

I'm pretty sure this isn't possible, but I thought it is worth asking.

I have two FreeNAS servers (A) and (B).
(A) is my primary server
(B) is a ZFS replication target

(A) has several heavily-used datasets that are relatively static and shared read-only via CIFS.
I'm tempted to reduce load on (A) by sharing these datasets on (B) as well. At present I'm planning to just map some users to (A) and others to (B).

Is there a way to dynamically load-balance between (A) and (B) for these...

Load balancing a couple of CIFS shares