If you're trying to do real time image processing captured with a Webcam, you should start thinking changing to other programming lenguage. VB is really slow...
Basically, you can get a pixel value of a PictureBox control using the Point function.
Ex.:
Msgbox Picture1.Point(100,100)
It will return the pixel 100,100 color value as a Long.
Starting from there, you can implement algorithms to detect patterns or movement(ammount of pixels changed since previous image).
Se yaaa!