Update this:
$UpdateQuery->addFilter($MultipleUpdateIndexColumn, "=", $MultipleUpdateIndexColumnType, $_POST[$MultipleUpdateIdentifier."_".$MultipleUpdateCount]);
to this:
$UpdateQuery->addFilter($MultipleUpdateIndexColumn, "=", $MultipleUpdateIndexColumnType, $_POST["Shawn_wamultihidden_".$MultipleUpdateCount]);
and update this:
<input type="hidden" name="Shawn_wamultihidden[]" id="Shawn_wamultihidden_<?php echo($wa_startindex); ?>" value="1" />
to this:
<input type="hidden" name="Shawn_wamultihidden_<?php echo($wa_startindex); ?>" id="Shawn_wamultihidden_<?php echo($wa_startindex); ?>" value="<?php echo($rs_ordersinfo->getColumnVal('DetailID')); ?>" />