вот код
[xfgiven_serials]<center>
<sc ript language="javascript">
<!--
function showhideBlocks(val)
{
if (val<=series) document.getElementById('ifr').src = arr[val-1];
}

var start = 1;
function fun()
{
if (start==0) return;
start = 0;
for(i=2; i<=series; ++i)
{
var newSelectOption = document.createElement('option');
newSelectOption.setAttribute('value', i);
textForOption=document.createTextNode("Серия "+i);
newSelectOption.appendChild(textForOption);
document.getElementById('series').appendChild(newSelectO
ption);
}
}

var arr = [[xfvalue_serials]];


var series = arr.length;
-->
</script>

<center>
<div style="margin-bottom:10px">
<ifr ame id="ifr" src="[xfvalue_serials1]" frameborder="0" height="475" width="720"></iframe>
</div>

<center>
<select id="series" onc lick="fun()" onc hange="showhideBlocks(value)" >
<option disabled selected>Выбирите серию</option>
<option value="1"> Серия 1
</option></select></center></center>
</center>
<br>
<center></center>[/xfgiven_serials]