DHCP give proxy info to pxe client ??

We have many dhcp servers on remote sites and want the possibility
to boot from a central imaging server.
Is it possible to tell dhcp client which ip adress the imaging proxy server
have?
(dhcp servers are nw 5.1)

We want pxe boot in our wan to a central zenworks imaging server.
(to get the policy in zen 7).

Any solution ?

Magne