In SX3, go to your punch-in time, hold the "alt" key while clicking on the "L" on the transport bar.... go to punch-out time, hold "alt" and clcik the "R" on the transport bar. now, click the little weird line thingy below the "L" and "R" so they light up... then record-enable your track, then rewind to your desired playback start position, press play, but not record .... it will punch in and out automatically... it's pretty sweet.