Try adding to the select onChange="alert(this.options[this.selectedIndex].value);"
as a starting point to move you forward.
Using JQuery is not the answer, its is not JavaScript yet it relies heavily on its use.
echo '<select name="evaluator" id="evaluator" onChange="alert(this.options[this.selectedIndex].value);">';
Then when your select has a change, the value of what was selected should appear in a pop up alert box.
Accessing a DOM entity is as easy as... document.formName.formElement or in your case document.selectStaff.evaluator then from that you can access the various elements like the .options[] array and the .selectedIndex (which is the reference to the actual selected array element.
See this example code from a select query
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title></title>
<body>
<script type="text/javascript">
place = {
Davidson:['Antioch', 'Nashville'],
Rutherford:['Smyrna', 'LaVergne']
}
function clearOpts(target){
sel = document.info[target].options;
for (i = sel.length - 1; i >= 0; i--)
sel.remove(i);
}
function configureDropDownLists(o,city) {
if(document.info[city].options.length!=0) clearOpts(city);
selected = o.selectedIndex;
if(selected==0) return;
city = o.options[selected].value;
console.log(">" + city);
for (i = 0; i < place[city].length; i++) {
createOption('city', place[county.value][i], place[county.value][i])
}
}
function createOption(target, label, value) {
opts = document.info[target];
opts.options.add(new Option(label,value) );
}
</script>
<form name="info">
<tr>
<td>County Name: </td>
<td><select name="county" id="county" onChange="configureDropDownLists(this,'city');">
<option value=""></option>
<option value="Davidson">Davidson</option>
<option value="Rutherford">Rutherford</option>
</select></td>
</tr><br>
<tr>
<td>City: </td>
<td><select name="city" id="city">
</select></td>
</tr>
</form>
</body>
</html>
From that you should be able to find what you need.