hmmm, ok, try changing this line:
if ((strpos((",".ValidatedField("pluginnew_788","pluginnew_788").","), "," . "3" . ",") !== false || "3" == "")) {
to:
if ((strpos((",".ValidatedField("pluginnew_788","pluginnew_788").","), "," . "3" . ",") !== false || "3" == "") && !(strpos((",".ValidatedField("pluginnew_788","pluginnew_788").","), "," . "1" . ",") !== false || "1" == "")) {