You mean the parent script is running in windows and you want it to call a pre-existing script on a different box running a UNIX system?
There are several ways to do this(after all TIMTWTDI). It would really depends what kind of connection there is between the two boxes for what the best way to handle it is. Are you running file-shares between the two? Telnet? SSH? The best way to do it is going to depend on what kind of access you have available.