Build up a full routing capaciity in PIX

I have installed several Cisco PIX in HQ and different branch offices. Say HQ (192.168.1.0) BranchA (192.168.20.0), Branch B (192.168.30.0). Internet is the only WAN link connecting each Branchs office and HQ.

When my VPN client connecting ot HQ PIX, it could only route to the server located 192.168.1.0. Is there any way to configure my HQ PIX (or additional with any equipment) so that this VPN client could able to route to other Branch office through the HQ PIX.

My HQ has already divided in serveral VLAN. (192.168.2.0, 192.168.3.0) inaddition to 192.168.1.0. If I install a local router on my HQ which could allow it to route across these VLANs and my local lan. Afterwards, I install a static route in my HQ PIX. Could then allow my remote Cisco VPN client to access these VLAN once they form a tunnel with my  HQ PIX ?

HQ PIX (192.168.1.10)
route inside 192.168.2.0 255.255.255.0 [internal router]  -> enable VPN client to VLAN1
route inside 192.168.3.0 255.255.255.0 [internal router]  -> enable VPN client to VLAN2