OK, Change that to:
<option value="<?php echo $row_WADADynListunits['unit_id']?>" <?php if (!(strcmp("". $row_WADADynListunits['unit_id']."", (isset($_GET["invalid"])?ValidatedField("HandlerInsert","unit"):"")))) {echo "selected=\"selected\"";} ?>><?php echo $row_WADADynListunits['unit_name']?></option>