attachInterrupt() / detachInterrupt()

I have not being sussecifuly in use attachInterrupt() to implement a Cronometer with Arduino Duimilanove.
May someone help me?

#include <LiquidCrystal.h>
LiquidCrystal lcd(12,11,10,9,8,7,6);
volatile float vetor[3] = {0,0,0};
volatile int inc = 1;
void setup(){
lcd.begin(16,2);
lcd.setCursor(0,0);
lcd.print(" Interrupt ");
delay(1000);
lcd.clear();
}
void incre(){
inc = inc++;
seleciona();
attachInterrupt(0, incre, CHANGE);
detachInterrupt(0);
}
void seleciona(){
switch (inc){
case 1:
vetor[inc] = (millis()/100);
break;
case 2:
vetor[inc] = (millis()/100);
break;
default:
inc = 1;
break;
}
vetor[3] = vetor[2] - vetor[1];
}
void loop(){
lcd.setCursor(0,0);
lcd.print("A ");
lcd.print(vetor[2]);
lcd.setCursor(8,0);
lcd.print("B ");
lcd.print(vetor[1]);
lcd.setCursor(0,1);
lcd.print("DIF ");
lcd.print(vetor[3]);
}

You have to call the attach in part of the code that is actually executed, like setup

Please use the # button when posting code.

Also, don't put the attach interrupt call inside the function being attached.