Quadrature Decoder - I asked for the wrong thing

I was in the middle of building Mariss' quadrature decoder with the
4077 chip when I realized that this won't do what I want.
I really need to take the quadrature signals from the encoder and
send them to the PC as jog signals from the keyboard.
If I did what I wanted to initially, the controller would loose track
of the machine coordinate system since I would be sending step/dir
signals without the controller's knowledge.

Can anyone point to the "way" to emulate keystrokes from quadrature
signals? I plan on having a switch that will enable/disable the
keyboard in favor of the pulse generator during jogging. This way
the control stays "in control"

Thanks for the help.
Joe V.