Need super Dos geek

I’m trying to write a dos batch that finds a PC’s location on our WAN. The NT machines are easy, but the 9X are posing a problem. We have several 24 and 26 bit subnets, so I need to isolate the third and fourth octate of the gateway and set it to a variable, or at least a “do goto “something”. I’ve seen examples of debug doing things like this, but I don’t understand the exe that well. Any help would be great.