dropdown list onchange problem

[CODE]
<script type=”text/javascript”>
function ni(form) {
ni=parseFloat(form.ni.value);
form.ans4.value = (form.lista1.value == “one”)?0.62 :
(form.lista1.value == “two”)?0.8 :
(form.lista1.value == “three”) ?0.9 :

‘error’;
}

var ni;
var error;
if (form.lista1.value == “one”)
{
document.write(ni=0.62);
}
else if (form.lista1.value == “two”)
{
document.write(ni=0.8);
}
else if (form.lista1.value == “three”)
{
document.write(ni=0.9);
}

else
{

document.write(error);
}
</script>

<FORM name=”form2″>
<table width=”93″ border=”1″>
<tr>
<td colspan=”2″>formula</td>
</tr>
<tr>
<td height=”66″ colspan=”2″><div align=”center”>
<select name=”lista1″ size=”1″ id=”lista1″ onchange=”javascript: dropdownlist(this.options[this.selectedIndex].value);”>
<option value=”one”>one</option>
<option value=”two”>two</option>
<option value=”three”>three</option>
</select>
</div></td>
<tr>
<td>ni =</td>
<td><input type “number” value=”” name=”ans4″ size=”9″ /></td>
</tr>

</table>
</FORM>
[/CODE]

What am i doing wrong?

i want to display values in textbox on select…when user select one it should write 0.62 etc…
pls help

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