It's easier to do it with an Image.RotateFlip statement:

Code:
'to rotate 90 degrees clockwise:

PictureBox1.Image.RotateFlip(RotateFlipType.Rotate90FlipNone) 

'to rotate 90 degrees anticlockwise: 
PictureBox1.Image.RotateFlip(RotateFlipType.Rotate270FlipNone)
BB