The follow buttons change the interval

<button onclick='$(".slidetabs").data("slideshow").stop();$(".slidetabs").slideshow().getConf().interval = 5000;$(".slidetabs").data("slideshow").play();'>5 seconds Interval</button>

<button onclick='$(".slidetabs").data("slideshow").stop();$(".slidetabs").slideshow().getConf().interval = 1000;$(".slidetabs").data("slideshow").play();'>1 second Interval</button>