You're up a bit late, aren't cha? (Or early? Do programmers
ever get to see the sun?)
I think it's
rc_dig_in03.
Here's some code we had from last year, using joystick 2 y-axis to move the grabber arm up or down (like your lower arm with the motor at the elbow). We had a limit switch (LS) at the top and bottom to stop the motor, but allows it to go the other way even if it reaches the limit switch.
Code:
//-------------------------- ARM WORK 3 -------------------------------------
//Arm desired direction is from JoyStick2, Y-axis. UP goes fwd, DOWN is back.
//pwm05 is the motor. LimitSwitch 5 and 7 is fwd and back stop points.
//Change pwm numbers of motor, LS, and Joystick as need be.
if (p2_y >(127+50)) //If Joystk2 Y pushed up - arm forward
{
if (rc_dig_in05 == 0) //is LS5 not pressed?
{ pwm05= 127+3; } // No- turn motor on!
else
{ pwm05= 127; } // Yes- turn motor off!
}
else if (p2_y < (127-50)) //If Joystk2 Y pulled back - arm backwrd
{
if (rc_dig_in07 == 0) //is LS7 not pressed?
{ pwm05= 127-3; } // No- turn motor on!
else
{ pwm05= 127; } // Yes- turn motor off!
}
else
{ pwm05= 127; } //Turn motor off
Of course if you're doing autonomous, don't use the joystick!

Just remember to cover all possibilities (all if/ifelse/else's) so you
know at the end the motors are on or off.
This wasn't our final code, but it did work at the time. As always YMMV.
______________________
One of the main causes of the fall of the Roman Empire was that, lacking zero, they had no way to indicate successful termination of their C programs.