Well, there's another way to skin this cat.
(I'd first try specifying multiple routes in that route field, but if that fails, do this:)
Give the remote site a static remote IP address, and then create 4 static routes whose next hop is that static IP.
So if you set remote-address=192.168.255.254 (or whatever) in the secret, create as many static routes as you like, but with that IP as the next hop. You could even create a black hole route for 192.168.255.254/32 with a distance of 254 so that whenever the VPN is down, the remote networks are also routed to the black hole and not out your Internet connection.
Or - if the remote networks are all part of a contiguous supernet, route that supernet:
192.168.4.0/22 = 192.168.4.0 - 192.168.7.255
Or if you're really feeling froggy, enable OSPF on the VPN.
I have 4 LAN's that I need to access on the other end, as you can see in my previous post. How can I add the 4 LAN's in the route field?
EDIT: I've tested this in my lab, and you can specify multiple routes in the PPP secret - just put them in separated by commas. e.g.: 192.168.10.0/24,192.168.55.0/24,172.16.0.0/16