blockproc and find best matching block with drms

i have problem with my work with matlab. i would like to know how to find best matching block with Drms. before that, i have to divide rgb image (64x64) to overlapping blocks (16*16) and nonoverlapping blocks (8x8) and transform it to gray images. my problem is, how to compare every block between nonoverlapping and overlapping and to get result of Drms ? every block in non overlapping block must be compare to every block in overlapping blocks. this is my program, hopefully you can help me. thanks..

clear all;
clc;

gambar=imread('lena.jpeg');

r=gambar(:,:,1);
g=gambar(:,:,2);
b=gambar(:,:,3);

r=rgb2gray(gambar)

fun = @(block_struct) (block_struct.data, );

q=blockproc(r,[16 16],fun);

fun = @(block_struct) (block_struct.data, );

p=blockproc(r,[8 8],fun);

a=1;

x=1;

while a<50;

      for b=a:(15+a)

         c=b

      end;

      a=a+4;

end;

             while x<50;

          for y=x:(15+x)

              z=y

          end;

              x=x+4;

      end;

i don't have idea to put what function i should put in fun