Um.
Think about what you are trying to do: you are trying to get the IP address of a computer via your network, which means you need the IP address in order to talk to it...
This may help:
Retrieving IP and MAC addresses for a LAN[
^] - it's in C#, but online convertes can sort that for you (or better, leave it in C# and put it in it's own assembly - you can then call the methods from VB without any problems).