To find out which step the loop is processing, you can always click pause and check "k" and "j".
However, you can also add few lines of command to automatically inform you the process.
for k = 1:100
if mod(k,10) == 0
fprintf(['Processed: k=' num2str(k) '\n']);
for j = 1:500
if mod(j,50) == 0
fprintf(['j=' num2str(j) ' processed \n']);
the above code will give you the value of "k" whenever it becomes the multiple of 10 (i.e. 10, 20, 30, and so on) and the value of "j" when it becomes the multiple of 50.
Hope this helps!