A strip of tape (masking tape or packing tape - some kind that's not too sticky) placed on the counter in the spots where they jump up can be deterrent. The trick is to put the tape sticky side up (tape it down on the ends with a couple other pieces). They'll jump up, and absolutely hate the feeling of something sticky on their paws. You should only need to do this for a few days. If they're intelligent and not too stubborn, they'll take the hint. Very headstrong or dumb cats may never learn, unfortunately...