search form to search two columns from mssql table

Hi we have a inhouse Win32 application that saves data to MSSQL. I am trying to create a php search form that will search a table which has following data.

my search form

<form name="myform" method="post" action="searchresults.php" id="myform">
<input type="text" name="search" size=30>
<Select NAME="field">
<Option VALUE="contents">Contents</option>
<Option VALUE="item_id">Item Number</option>
</Select>
<input name="Search" type="Submit" id="Search" value="Search">
</form>

my search results page

<?php 
include 'includes/opendb.php';

$search = $_POST['search'];
$field = $_POST['field'];
if ($search == ""){ 
    echo "<p>You forgot to enter a search term"; 
    exit; 
}

$result = mssql_query("SELECT * FROM dbo.userAnswers WHERE {$field} LIKE '%{$search}%'"); 

echo '<ul class="SearchResults">';
while($r = mssql_fetch_array($result)){
    $item_id = $r['item_id'];
    $contents = $r['contents'];
    echo <<<LIST
        <li>
            <ul class="Result">
				<li>{$item_id}</li>
				<li>{$contents}</li>
            </ul>
        </li>
LIST;
}
echo '</ul>';
?>
<?php
include 'includes/closedb.php'; 
?>

I now have changed my search form to be like this. When someone select Firstname from dropdown list I want the search to be done for all the 101 item id and its contents.

<form name="myform" method="post" action="searchresults.php" id="myform">
<input type="text" name="search" size=30>
<Select NAME="field">
<Option VALUE="101">Firstname</option>
<Option VALUE="102">Start Date</option>
<Option VALUE="103">Introduction</option>
<Option VALUE="104">Question 1</option>
<Option VALUE="105">Question 2</option>
</Select>
<input name="Search" type="Submit" id="Search" value="Search">
</form>

What changes I will be looking to do in my search results page script. I have tried changing few bits like this but nothing is displayed in the search results page.

Your help will be much appreciated thank you.

<?php
include 'includes/opendb.php';

$search = $_POST['search'];
$field = $_POST['field'];
if ($search == ""){
    echo "<p>You forgot to enter a search term";
    exit;
}

$result = mssql_query("SELECT * FROM dbo.userAnswers
WHERE item_id = $field
AND contents LIKE '%{$search}%'
");


echo '<ul class="SearchResults">';
while($r = mssql_fetch_array($result)){
    $item_id = $r['item_id'];
    $contents = $r['contents'];
    echo <<<LIST
        <li>
            <ul class="Result">
                <li>{$item_id}</li>
                <li>{$contents}</li>
            </ul>
        </li>
LIST;
}
echo '</ul>';
?>
<?php
include 'includes/closedb.php';
?>