C#

// define variables to hold calculated
// sizes, and positions for PictureBox
private int pbSizeIncrement = 12;

private Size pbBaseSize;
private Size pbEnterSize;
private Point pbBaseLocation;
private Point pbEnterLocation;

// in your Form's Load EventHandler
// pre-calculate Size, and Location
// for your PictureBox
private void Form1_Load(object sender, EventArgs e)
{
    pbBaseSize = pictureBox1.Size;
    pbEnterSize = new Size(pbBaseSize.Width + pbSizeIncrement, pbBaseSize.Height + pbSizeIncrement);

    pbBaseLocation = pictureBox1.Location;
    pbEnterLocation = pbBaseLocation;
    pbEnterLocation.Offset(pbSizeIncrement / -2, pbSizeIncrement / -2);
}

// use calculated values in your EventHandlers
private void pictureBox1_MouseEnter(object sender, EventArgs e)
{
    pictureBox1.Size = pbEnterSize;
    pictureBox1.Location = pbEnterLocation;
}

private void pictureBox1_MouseLeave(object sender, EventArgs e)
{
    pictureBox1.Size = pbBaseSize;
    pictureBox1.Location = pbBaseLocation;
}

private void pictureBox1_MouseEnter(object sender, EventArgs e)
{
    pictureBox2.Visible = true;
    pictureBox1.Visible = false;
}

private void pictureBox2_MouseLeave(object sender, EventArgs e)
{
    pictureBox1.Visible = true;
    pictureBox2.Visible = false;
}

byte sum = 0;
foreach (byte b in myData)
   {
   sum += b;
   }