I would be happy to script this even without a fee, I just don't have the time at the moment.
Also, make sure you understand, the original poster was wanting to track event logs forwarded from computers with dynamic IP addresses, I don't know that there are any good reasons to have switches or other network devices use DHCP, but this would likely not work for them.
There might also be an easier way I just thought of too...
Don't the event log messages include the hostname of the PC they are coming from? If that's the case you could just filter message text looking for hostname and avoid scripting all-together.