error in steganography using dct

Error in finding b and c...what is the error? please help

I = imread('cameraman.tif'); I2=imread('F:\watermark.jpg');

subplot(2,2,1),imshow(I); subplot(2,2,2),imshow(I2); T=dctmtx(8); fun = @(block_struct) dct2(block_struct.data); B = blockproc(I,[8 8],fun);

k=0; for i=1:256 for j=1:256 if B(i,j)>0

              b=dec2bin(typecast(single(B(i,j)),'uint32'),32);
              b(1,7:8)=I2(1,mtimes(k,2)+1,mtimes(k,2)+2);
              k=k+1;
              c=double(typecast(uint32(bin2dec(b)),'single') );
              B(i,j)=c;
          end
      end
end

[Jan]

Please post the complete error message.