Desplegar checkbox segun combo

[Toninito]

Gracias

tengo este codigo por si a alguien le sirve

Código HTML:

JAVASCRIPT
<script type='text/javascript'>
function showDiv(idOfDiv) {
document.getElementById(idOfDiv).style.display = 'block';
}
function hideDiv(idOfDiv) {
document.getElementById(idOfDiv).style.display = 'none';
}
</script>
 
HTML:
 
<select>
<option name="fieldName" id="field1" onclick="showDiv('AirOptions'); hideDiv('OceanOptions'); hideDiv('DomesticOptions');" onblur="hideDiv('div1');" selected="selected"/>Air Service</option>
<option name="fieldName" id="field2" onclick="showDiv('OceanOptions'); hideDiv('AirOptions'); hideDiv('DomesticOptions');">Ocean Service</option>
<option name="fieldName" id="field3" onclick="showDiv('DomesticOptions'); hideDiv('AirOptions'); hideDiv('OceanOptions');" onblur="hideDiv('div3');">Domestic Service</option>
</select>
 
<div id="AirOptions" style="display:none;">Air Services</div>
<div id="OceanOptions" style="display:none;">Ocean Services</div>
<div id="DomesticOptions" style="display:none">Domestic Services</div>