help on QB multi site sharing

Computer A: Win XP pro, DSL through a router
Computer B: Win XP home, DSL through a router
A and B are miles away. Both have Quick Books pro installed.

Now I know: Enable A as a host by turning on the remote desktop. Establish a VPN between A and B. Create a remote desktop connection to log on B.

Questions: Will this allow Quickbook pro in A and B (it has multi user mode) access the the same company file in A simultaneously?
If the DSL has dynamic IPs, will it reset the VPN and remote connections after every reboot? And if so how to avoid it?
Any other more detailed advice?

Thanks A lot!