VPN and static routing issue

I've configured RRAS on a 2003 server SBS in a LAN+DMZ environment:

LAN:
192.168.0.0/24 gw 192.168.0.254

DMZ:
10.100.1.0/24 gw 10.100.1.254

Both subnets are managed via a firewall (the gw for both subnets)
To VPN clients I assigned the range 192.168.0.100-129, and on client side I
disabled the "remote gatway" option to let clients use their own connection
to surf the web.

My issue is that clients can't connect to 10.100.1.0 subnet since they don't
have the static route. Meantime I can't add a persistent static route since
clients get a dynamic IP on each connection.
I tried with the option available for domanin user under the "incominc call"
(I apologize not using the right terms but my OS is in Italian!) to add
static routes, but it simply doesn't seem to work..

Any suggestion about how to assing a static route to the VPN clients?

Many thanks.

-f