VS 2010 Array index reference

Hi, using Visual Basic 2010 Express, I created a checkerboard using Dim Board(64) As PictureBox then assigned each cell an image and last added it to form1 in a loop Me.Controls.Add(board(x)). Worked fine. When a cell of the checkerboard is clicked I need to know the index of the cell. How do I reference the index of the cell so that I can use it in changing the image and other calculations? Your assistance is highly appreciated.