Selecting the maximum value of a cell within a specific range, x number of times?

Hi,

I'm new to matlab but will be using this to build an agent based model. I have a matrix (M), and a starting position (xpos=5 , ypos=5). I need to select the cell with the maximum value within a distance of 3 cells in every direction of the starting position, and repeat this 10 times. I am using a reference code, but I can't seem to figure out what the following two lines of code mean within the larger script:

distance = sqrt((ystart+ii-5)^2 + (xstart+jj-5)^2);  

            if M(ystart + ii,xstart + jj) > maxevi

I know this is the formula for the distance between two points, but I'm not sure why you have to subtract the "5", which is the starting position in the matrix. Here is the full code to select the highest value within a certain distance, 10 times:

for i=1:maxtime  %maxtime would be 10
    xstart=xpos-range  %range would be 3 cells
    ystart=ypos-range
    max=0           %this sets the maximum value to 0
    maxx=xstart
    maxy=ystart

for jj=1:6
    for ii=1:6 %to cover the range of 3 for all directions of the starting position each time

          distance = sqrt((ystart+ii-5)^2 + (xstart+jj-5)^2);  

          if M(ystart + ii,xstart + jj) > maxevi        
              maxevi = M(ystart + ii,xstart + jj);
              maxx = xstart + jj;
              maxy = ystart + ii;
          end
      end
  end

[Andrew Newell]

Equally puzzling: it doesn't change the value of max.