Multiple search domains via DHCP?

Is it possible to have Mac's DHCP server software to send more than one search domain to clients? Currently the GUI just has a field 'Default Search Domain' under each subnet, but we really need to be able to specify two search domains. We also don't want to manually configure this on a per-client basis.

I've tried entering more than one domain in Default Search Domain, separated by spaces and commas, but neither propagated both domains to clients. Any ideas would be greatly appreciated!