Help: how do I clear client arp cache?

Hi

I'm very new to this as I was just asked to modify someone else's code. I don't know much about Nullsoft, but all I need to do is add a line in the current script that will clear the arp cache of a windows client. The command to do so is:
arp -d *

Does anyone know how I can do this?

Thanks

Matt

availabe on >=w2k