How to apply calibration code to actual Accelerometer method?

After a google or two, I came up with this code to save the current position the user is in and save it to NSUserDefaults. This is in my settings view: Code:

//Add code for calibrating accelerometer
        UIAcceleration *acceleration;
        float accelX = (acceleration.x - [[NSUserDefaults standardUserDefaults] floatForKey:@"X-Calibrate"]);
        float accelY = (acceleration.y - [[NSUserDefaults standardUserDefaults] floatForKey:@"Y-Calibrate"]);
        [[NSUserDefaults standardUserDefaults] setFloat:accelX forKey:@"X-Calibrate"];
        [[NSUserDefaults standardUserDefaults] setFloat:accelY forKey:@"Y-Calibrate"];

To reset the calibration I do: Code:

[[NSUserDefaults standardUserDefaults] setFloat:0 forKey:@"X-Calibrate"];
    [[NSUserDefaults standardUserDefaults] setFloat:0 forKey:@"Y-Calibrate"];

Now here is where I need a slight bit of help. Now that I have these values in NSUserDefaults. How would I apply it to the following code so that the calibration is 'fully' implemented? Here is the code for the accelerometer currently: Code:

- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceration {
    AccelPoint.x += (acceration.x*50);
    if (AccelPoint.x < 0) {
        AccelPoint.x = 320;
    }
    if (AccelPoint.x > 320) {
        AccelPoint.x = 0;
    }
    playerSpeed += 0.066;
    AccelPoint.y += playerSpeed;
    Square.center = AccelPoint; 
}

This is some of the variables and how 开发者_如何学JAVAthey are defined: Code:

CGPoint AccelPoint;
float playerSpeed;

Thanks!

Also quick little site question for that accelerometer code, should I be using if-elseif? Would that be more efficient or should I leave it at if-if?