Keypad Library... Returning a string after user pressed a certain character

Hey guys,
and thank you Arrch
Well so far i took matter in my hands and started writing.
I was able to store characters in a buffer and have it return a string when the buffer is full and clearing the buffer. I will now just need to get the butter return when a certain key is pressed.
Suggestions are always welcome.
Thanks again
the code so far

/* @file CustomKeypad.pde
|| @version 1.0
|| @author Alexander Brevig
|| @contact alexanderbrevig@gmail.com
||
|| @description
|| | Demonstrates changing the keypad size and key values.
|| #
*/
#include <Keypad.h>
char buffer[6];
int i;
const byte ROWS = 2; //four rows
const byte COLS = 3; //four columns
//define the cymbols on the buttons of the keypads
char hexaKeys[ROWS][COLS] = {
  {'A','B','C'},
  {'D','E','F'}
  
};
byte rowPins[ROWS] = {9,8 }; //connect to the row pinouts of the keypad
byte colPins[COLS] = {7, 6, 5}; //connect to the column pinouts of the keypad

//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS); 

void setup(){
  Serial.begin(9600);
}
  
void loop(){
  while( i < sizeof(buffer))
  {
    
  buffer[i] = customKeypad.getKey();
  if (buffer[i] == '\0')
    break;
    i++;
   if ( i == sizeof(buffer))
    {
      Serial.println(buffer);
      buffer[i]=0;
      Serial.println("-------------");
      break;
    }
   
  }
}

Image of serial Monitor is attached.