Fixing a for loop that's 90% correct

On the first pass through k, everything is fine. But when k=2, x=2, so my subscript index is starting with 2, not 1. If I change 'for x = k:ssLength(k)' to 'for 1 = k:ssLength(k)', then the loop starts at 1 on each iteration, but doing this overwrites the data in the cell, instead of appending to it.

 i=2:91;
  j=9:97;
  for k = 1:length(matrix)
      for x = k:ssLength(k)
          m1(i(k),j(x))=-mid(shortStrikeIdx{1,k}(x))+mid(longStrikeIdx{1,k}(x));
      end
  end

[Walter Roberson]

?? That codes does not write to any cell and does not append to any cell, so I do not understand your description.