add check box to a drop down list

I've created a multiple drop down list from my database. Instead of having to hold down the Ctrl key to select multiple selection can I have a check box instead? Here's my current code:

<tr>
<td><label>Select Events:</label></td>
<br>
<td>Use Ctrl Key for multiple</label></td>
<br>
<td>
<select name="eventn[]" size="12" multiple="multiple">
<?php

$sql="Select * from eventmaster";
$result = $conn->query($sql);

while ($row = mysqli_fetch_array($result)) {

echo "<option value=$row[eventnumber]>$row[eventname] . $$row[eventamount]  . $row[eventdate]</option>";

}
?>
</select>
</td>
</tr>   
<br>
<tr>

</div>

As I mentioned before I'm new to this so any help is appreciated.

Thanks