Dimensional Std along third dimension

Dear All, I have a sequence of images, saved in a three dimension matrix (480X640X64). I need to calculate the standard deviation along the third dimension: Image_Std = std(Image, 0, 3) but matlab is always out of memory. I do not want to use a for..loop (ugly ..:-)) How can I trick matlab? I have a 32bit OS

Thanks Avner Mediouni R&D Physicist