multiple backhand clusters on one subnet?

We're considering using mod_backhand for load balancing on our cluster of
webmail servers. As we're also considering backhand for load balancing on the
servers that host our directory client, we only want them sharing their
candidacy information with other servers in the same service (eg mail requests
shouldn't get shunted to a directory server and vice versa).

The IP addresses for each service are non-contiguous, and both are on the same
subnet.  Is it possible to place the machines in separate pools?  If so, how?

thx
Liam