Use a specific key or button to control incrementation of boucle for

Hello, I am planing to use a key or button to activate or deactivate incrementation of boucle for. Code:

int LEDcontrol=3; // LED on pin # 3
int VoltRead=4; // A voltmeter on pin # 4 (not in the subject)
int commande=(0,DEC); // Use to sand a commande to activate or deactivate boucle for
void setup(){
pinMode(3, OUTPUT); // Configuration of digital port # 3
pinMode(4, INPUT);
Serial.begin(115200);
}

void loop(){
commande=Serial.read(); //Reads a commande of a key
if(Serial.available()==97){ //If is sent, do gradual incrementation on PWM to turn DEL on
do{
for(int i=0; i<=255; i++){
digitalWrite(3,HIGH);
}
while(Serial.read()==commande); //Execute function till the
is pressed
}
}

commande=Serial.read();
if(Serial.available()==115){ //Reads a commande of a key
do{
for(int i=255; i>=0; i–){ //If is sent, do gradual decrementation on PWM to turn DEL off
digitalWrite(3,HIGH);
}
while(Serial.read()==commande); //Execute function till the is pressed

//commande=Serial.read();

delay(500);
}

Deja vu all over again ?
http://arduino.cc/forum/index.php/topic,157101.msg1176858.html#msg1176858