getting <select> value

Hi, I am trying to get the value in a select box then append it the end of a URL.

I have my form as so:

HTML Code:

---

<form name="formorder">
<select name="selectorder" onChange="order()">
<option value="atoz">A-Z</option>
<option value="ztoz">Z-A</option>
<option value="dateadded">date added</option>
<option value="dateedited">date edited</option>
</select>
</form>

---

and i have my javascript in the head of my page:

HTML Code:

---

function order() {
        neworder = document.formorder.selectorder.options[document.formorder.selectorder.selectedIndex].value;
        location.href="<?php echo $referer ?>" + "?orderby=" + neworder;
}

---

The PHP variable $referer is the URL of the previous page.

I'm getting the error 'Object expected' and i can't figure out why. It says the error is on line 251 but i only have 230 lines in my code :-S

Any help would be greatly appreciated :) thanks, BIOSTALL