You can combine this all into a long command line, but let's split it up for clarity:
col2select = info(:,2) < 100 & info(:,2) ~= 0;
col3select = [0; diff(info(:,3))] == 20;
result = info(col2select & col3select, 1);
I assumed that you wanted only an exact increase in 20 from the previous line in column 3. It's easy to modify this to your needs.
This will output only the relevant rows. You can of course find the indices of those rows if you need:
indices = find(col2select & col3select);
-g-
