Here My edited setEngineSpeedDir function and Key press:
//DIFFERENTIAL STEERING: Motor 1: Left side Motor 2: Right side
void setEngineSpeedDir( signed char cNewMotorSpeedDir )
{
unsigned char cSpeedValDir_Motor1 = 0;
unsigned char cSpeedValDir_Motor2 = 0;
if( cNewMotorSpeedDir >= 100 )
{
cSpeedValDir_Motor1 = SABER_MOTOR1_FULL_FORWARD; // GO RIGHT
cSpeedValDir_Motor2 = SABER_MOTOR2_FULL_STOP;
}
else if( cNewMotorSpeedDir <= -100 )
{
cSpeedValDir_Motor1 = SABER_MOTOR1_FULL_STOP; // GO LEFT
cSpeedValDir_Motor2 = SABER_MOTOR2_FULL_FORWARD;
}
}
else
{
// Calc motor 1 speed (Final value ranges from 64 to 127)
cSpeedValDir_Motor1 = map( cNewMotorSpeedDir,
-100,
100,
SABER_MOTOR1_FULL_STOP,
SABER_MOTOR1_FULL_FORWARD );
// Calc motor 2 speed (Final value ranges from 192 to 255)
cSpeedValDir_Motor2 = map( cNewMotorSpeedDir,
-100,
100,
SABER_MOTOR2_FULL_FORWARD,
SABER_MOTOR2_FULL_STOP);
}
// Fire the values off to the Sabertooth motor controller
SaberSerial.print( cSpeedValDir_Motor1, BYTE );
SaberSerial.print( cSpeedValDir_Motor2, BYTE );
void moveit( )
{
initSabertooth( );
}
void turn ( )
{
// Turn left
setEngineSpeedDir( -100 );
// Turn right
setEngineSpeedDir( 100 );
}
//KEY PRESS: (10/12/10)
void key()
{
signed char traverse;
signed char negotiate;
int buttonPin
if(Serial.available()>0) {
int data = Serial.read();
digitalWrite(buttonPin,LOW);
switch(data)
{
case'w':traverse = 100;break; //full forward
case's':traverse = -50;break; // half reverse
case'q':traverse = 0;break; // Stop
case'a':negotiate = -100;break; // left
case'd':negotiate = 100;break; // right
}
setEngineSpeed( traverse );
setEngineSpeedDir( negotiate );
}
{
But still with error: 
expected unqualified-id before 'else'
ketch_oct14a:181: error: expected unqualified-id before 'else'
sketch_oct14a:199: error: expected constructor, destructor, or type conversion before '.' token
sketch_oct14a:201: error: expected constructor, destructor, or type conversion before '.' token
sketch_oct14a.cpp: In function 'void key()':
sketch_oct14a:238: error: expected initializer before 'if'
sketch_oct14a:255: error: expected `}' at end of input
You have any clue?