[Alastor]

вот так вроде норм

<div id="cplayer1" style="display:block;"><iframe name='film_cinemas' id='film_cinemas' src='http://vk.com/video_ext.php?oid=177595935&id=162959834&hash=71483af4bb9b25b5&hd=3' width='307' height='260' frameborder='0'></iframe>
            <div class='vk_select'><button class="previous">&#8592</button><select size='1' onchange="javascript:if(document.getElementById('film_cinemas')) document.getElementById('film_cinemas').src=this.value;">
<option value='http://vk.com/video_ext.php?oid=177595935&id=162959834&hash=71483af4bb9b25b5&hd=3'>1 серия</option><option value="http://vk.com/video_ext.php?oid=177595935&id=162959836&hash=b095322a1122a202&hd=3">2 серия</option><option value="http://vk.com/video_ext.php?oid=177595935&id=162959838&hash=947cc72f8178eb3a&hd=3">3 серия</option><option value="http://vk.com/video_ext.php?oid=177595935&id=162959840&hash=c00fa8b2df9ead45&hd=3">4 серия</option>
</select>

<button class="next">&#8594</button>
</div></div>
<form name="test" method="post">
  <b>быстрый переход</b>
   <input type="text" size="1" maxlength=3 pattern="\d*" name="num">
  <input type="submit" value="ОК">
 </form>

<script>
window.addEventListener("DOMContentLoaded", function() {
    var d = document.querySelector("#cplayer1"),
    s = d.querySelector("select");
    d.addEventListener("click", function(b) {
     var a = b.target, i = s.selectedIndex;
     if(a.classList.contains("previous")) i-- ;
     else if(a.classList.contains("next")) i++  ;
     else return;
     if(i < 0) i = s.options.length - 1;
     i %= s.options.length;
     s.selectedIndex = i;
     s.onchange()
    })
	   var form =  document.test;
   form.onsubmit = function() {
   var i = (this.num.value - 1)||0 ;
   if(i < 0) i = 0;
   if(i > s.options.length - 1) i = s.options.length - 1;
   s.selectedIndex = i ;
   this.num.value = ++i;
   s.onchange();
   return false;
}

});


</script>