Thanks Jason - figured it out last night. Here is what I used:
<select name="ProductSportID[]" size="10" multiple id="ProductSportID">
<?php
do {
?>
<option value="<?php echo $row_WADADynListproductsports['SportID']?>"<?php if (!(strcmp($row_WADADynListproductsports['SportID'], WA_AB_returnPreSelectValue($WA_PreSelect_RelationalTable_1, $row_WADADynListproductsports['SportID'])))) {echo " selected=\"selected\"";} ?>><?php echo $row_WADADynListproductsports['SportName']?></option>
<?php
} while ($row_WADADynListproductsports = mysql_fetch_assoc($WADADynListproductsports));
$rows = mysql_num_rows($WADADynListproductsports);
if($rows > 0) {
mysql_data_seek($WADADynListproductsports, 0);
$row_WADADynListproductsports = mysql_fetch_assoc($WADADynListproductsports);
}
?>
</select>