function init()
{
    var selects = document.getElementsByTagName("select");
    var select;
    for(var i=0; i < selects.length; i++)
    {
        select = selects[i];
        if(select.id.indexOf("categoryListBox") >= 0)
        {
            select.onchange = onCategoryChange;
        }
    }
}

function onCategoryChange()
{
    setTimeout("__doPostBack('" + this.ID + "','')", 0);
}

function __doPostBack(eventTarget, eventArgument) 
{
    var theForm = document.forms['aspnetForm'];
    if (!theForm) 
    {
        theForm = document.aspnetForm;
    }

    if (!theForm.onsubmit || (theForm.onsubmit() != false)) 
    {
        theForm.__EVENTTARGET.value = eventTarget;
        theForm.__EVENTARGUMENT.value = eventArgument;
        theForm.submit();
    }
}