Is this any help?
Code:
<HTML>
<HEAD>
<script language="JavaScript">

function newpage() {
var f = document.frm1.site.options[document.frm1.site.selectedIndex].value

if(document.frm1.r1[0].checked){
	f += '1.html'
	
}else if(document.frm1.r1[1].checked){
	f += '2.html'
}else{

	alert("Select option")
	return false
}
	
parent.mainframe.location=f
}
</script>
<TITLE></TITLE>
</HEAD>

<BODY>
<form name="frm1" target="mainframe">
<select name="site" size="1" onchange="newpage();"
align="left">
<option selected>Afdeling.... </option>
<option value='tot'>Tot</option>
<option value='mar'>Mar</option>
<option value='mam'>Mam</option>
<option value='oma'>Oma</option>
<option value='bes'>Bes</option>
<option value='sja'>Sja</option>
</select>
<INPUT type=radio name=r1>
<INPUT type=radio name=r1>
</form>
</BODY>
</HTML>