'485 isn't really that much different from 232. The main differences are the ability to multidrop and good noise resistance since they use balanced transmissions.

If it's 4 wire 485 then one pair will be transmit from a master and connect to the receive of all the slaves. In turn all the slaves transmit lines will connect in parallel to the master's receive.

To run multiple slaves in a multidrop environment they need to be setup so they only turn their transmitters on when they actually send stuff. Since the master is the only device transmitting on the first pair it doesn't matter if it's setup like this or not. Actually if you want more than one master you'll need to setup transmit enable.

Soooo... assuming the master really is setup for transmit enable you can actually join the two pairs together to make the system 2 wire. The units might get confused though since they begin to see what they are transmitting.

Basically you'll need a 485-232 converter so you can plug it into your standard PC serial port. I haven't ever looked at the possibility of a simple 232-485 converter so you'll be up for some dollars.

If the 2 wire thing works, you'll only need one converter but if it doesn't and you want to snoop both lines, you'll need 2 x 232-485 converters.