arduino + lcd keypad shield df robot: how to change data from lcd and button?

Hi all!
I using arduino mega 2560 + lcd keypad shield df robot
I have a variable HighTemp
HighTemp = 70
I print it on LCD
Now, how to click button select to value 70 flashing and click button up to HighTemp=HighTemp++ and click button down to HighTemp=HighTemp-- and value 70 change over button. Then click button select to exit change
Please help me

Use a state machine:

enum states {NORMAL, SELECTED} State = NORMAL;

void loop() {
    int button = whichever button is pressed;

     switch (State) {
case NORMAL:
       if (button == SELECT)
            State = SELECTED;
       break;

case SELECTED:
       if (button == UP)
           HighTemp++;
       else
       if (button == DOWN)
            HighTemp--;
     //  use BlinkWithoutDelay technique to blink the display
        if (button == SELECT) {
            Dispay the new value
            State = NORMAL;
        }
     break;
    }
}