If your "victim" is running Windows XP, you can use SysInternal's PSExec program (see here: http://www.microsoft.com/technet/sysinternals/utilities/psexec.mspx ) which will allow you to execute programs on a remote computer without having any software on there computer, providing you know the Administrator username/password.
Regarding making a BlitzPlus program that will do this, you could either make a GUI as a front end for the PsExec utility (however I nice one has already been done, see here) or you could take a client/server approach, whereby you could make a server listen on a port on your victim's computer, then when you want to do something, you can connect from a client program using TCP and send commands to be interpreted by the host application.
Regarding making a BlitzPlus program that will do this, you could either make a GUI as a front end for the PsExec utility (however I nice one has already been done, see here) or you could take a client/server approach, whereby you could make a server listen on a port on your victim's computer, then when you want to do something, you can connect from a client program using TCP and send commands to be interpreted by the host application.