Checkbox group

Hi Again Jason,
If I want to do an update for a list, what changes would I need to make to the code below so that when you do the update, the items in the list that were originally selected show up when doing the update?

Here's the code:

<label for="User_Update_group_1_ExpertiseAreas" class="sublabel" > ExpertiseAreas:</label>
<div class="errorGroup"> <span>
<select class="formListfield_Medium" name="User_Update_group_1_ExpertiseAreas[]" id="User_Update_group_1_ExpertiseAreas" tabindex="19" multiple="multiple">
<option value="">Please select your choices.....</option>
<?php
do {
?>
<option value="<?php echo $row_rsExpertise['ExpertiseField']?>"><?php echo $row_rsExpertise['ExpertiseField']?></option>
<?php
} while ($row_rsExpertise = mysql_fetch_assoc($rsExpertise));
$rows = mysql_num_rows($rsExpertise);
if($rows > 0) {
mysql_data_seek($rsExpertise, 0);
$row_rsExpertise = mysql_fetch_assoc($rsExpertise);
}
?>
</select>
</span></div>

Thanks Jason