This is more of a javascript question, rather than PHP, but here's something to get you started:
<FORM name="guideform">
<SELECT name="guidelinks">
<OPTION SELECTED value="http://place.com/page1.htm">Page 1
<OPTION value="http://place.com/page2.htm">Page2
</SELECT>
<INPUT type="button" name="go" value="Go!" onClick="window.location=document.guideform.guidelinks.options[document.guideform.guidelinks.selectedIndex].value"> </FORM>
If you want to point the link to a frame, replace "document." in the event handler with "nameofwindow.".
If you want a new window, write a function like this:
<script language="JavaScript">
function newwin() {
details = window.open("../relative/float.php3","details","toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=no,resizable=no,width=500,height=400");
details.focus();
}
</script>