What do mean exactly or what are you trying to do as far as voltage control?
The handshake signals can be set or reset, but the data pins are serial clocked in and out at the baud rate, to and from a parallel register.
Better still, an 8255 based I/O card may prove a better alternative, this is the type that Camsoft and others use for machine I/O.
See the
www.keithley.com site for details and they have C++ and VB6 example code.
Al.