Your PC Gameport can be used for custom Inputs.

I have below supplied the pinouts for the game port which I hope helps you with this.

I am currently using mine with a custom made strafing stick for quake/unreal etc.

I also use this with a microswitch to detect a drawer being opened on my desk (ment for POS)

Pin Name Dir Description
1 +5V > +5 VDC
2 /B1 < Button 1
3 X1 < Joystick 1 - X
4 GND > Ground
5 GND > Ground
6 Y1 < Joystick 1 - Y
7 /B2 < Button 2
8 +5V > +5 VDC
9 +5V > +5 VDC
10 /B4 < Button 4
11 X2 < Joystick 2 - X
12 GND > Ground
13 Y2 < Joystick 2 - Y
14 /B3 < Button 3
15 +5V > +5 VDC

Note: Direction is Computer relative Joystick.
Note: Use 100kohm resistor.