dropdown boxes

Can anyone help me change these checkboxes into a dropdown box?

function hilite_elem (checkbox, element_name)
{
var svgobj;
var svgstyle;
var svgdoc= document.levels.getSVGDocument();

// For each element, get the element’s style object, then set
// its visibility according to the state of the checkbox.

svgobj = svgdoc.getElementById(element_name);
svgstyle = svgobj.getStyle();
if (!checkbox.checked)
{
// Hide level.
svgstyle.setProperty(‘visibility’, ‘hidden’);
}
else
{
// SHow level.
svgstyle.setProperty(‘visibility’, ‘visible’);
}

}

// –>
</SCRIPT>
<FORM NAME=”hilite_form”>
<CENTER>
<P>
<TABLE BORDER=”0″ CELLPADDING=”0″ CELLSPACING=”2″ WIDTH=”1000″>
<TR>
<TD COLSPAN=”2″>Visible Levels:<BR>
&nbsp;</TD>
</TR>
<TR>
<TD><INPUT TYPE=”checkbox” VALUE=”” ONCLICK=”hilite_elem(this,’level1′)”>Level 1</TD>
<TD><INPUT TYPE=”checkbox” VALUE=”” ONCLICK=”hilite_elem(this,’level4′)”>Level 4</TD>
</TR>
<TR>
<TD><INPUT TYPE=”checkbox” VALUE=”” ONCLICK=”hilite_elem(this,’level2′)”>Level 2</TD>
<TD><INPUT TYPE=”checkbox” VALUE=”” ONCLICK=”hilite_elem(this,’level5′)”>Level 5</TD>
</TR>
<TR>
<TD><INPUT TYPE=”checkbox” VALUE=”” ONCLICK=”hilite_elem(this,’level3′)”>Level 3</TD>
<TD><INPUT TYPE=”checkbox” VALUE=”” ONCLICK=”hilite_elem(this,’level6′)”>Level 6</TD>
</TR>
</TABLE>
</CENTER>

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