BlackBerry trackball and LCD screen

Hi!
I'm now trying to do something more difficult and I'm stuck on the blackberry to LCD thing.

First the Y axis will not work in my case.
Ill have a 2 row LCD will valu on every side.

I want to change the value up and down when the balckberry trackball will be move up or down.
The problem I have it's to have specific value on the screen.
It's not constant number so this is why I dont know where to start.

If it was specific jump number (let say +10 every time) it will be easy.

lcd.print(blabla++)

This is my first step to change the number.
Tell me if i'm ok!!

// Set the cursor to the value from the BlackBerry
if(upState != digitalRead(upPin)){
//Incrace the position of the colum.
y_pos++;
upState = !upState;
}

if(downState != digitalRead(downPin)){
//Decrace the position of the colum
y_pos--;
downState = !downState;

}