route between vlans with snat

i don't quite get the problem. could you perhaps draw a picture or such? you have servers in VLAN4 that go out to the internet with a specific SNAT IP per server? how is the SNAT done? then you add VLAN5, where does the problem start? what do you want to do with VLAN5, reach the internet from there or get into it from VLAN4? if it is the last you might be able to do only do SNAT if you go to the big bad internet but not when you stay internal.