Código:
<script type="text/javascript"> var mfuente = new Array (1,8.135,0.76400030560012,1810) ;</script>
<div id="calculador">
<h2>Convertidor Moneda</h2>
<form action="" name="fcalc" id="fcalc">
Amount: <input type="text" onkeypress="if(event.keyCode == 13) { return false; }" onchange="javascript:calcula();" value="1.0" size="10" name="cantidad" /><br />
Result: <span id="resultado">8.135</span><br />
<label for="fuente">De: </label><select onchange="javascript:calcula();" id="fuente" name="fuente">
<option selected="selected" value="0">Parallel Dollar</option>
<option value="1">Bolívar Fuerte</option>
<option value="2">Euro</option>
<option value="5">Colombian Peso</option>
</select><br />
<label for="dest">A: </label><select onchange="javascript:calcula();" id="dest" name="dest">
<option value="0">Parallel Dollar</option>
<option selected="selected" value="1">Bolívar Fuerte</option>
<option value="2">Euro</option>
<option value="5">Colombian Peso</option>
</select><input type="button" onclick="javascript:calcula();" value="Calculate" name="Calculate" />
</form>
</div>