having phone number format correctly

[admin]

many time users just add the phone number as one long number this will make the field show it in a normal way xxx-xxx-xxxx

<input type="tel" pattern='\d{3}[\-]\d{3}[\-]\d{4}' name="contact_phone" class="forrmfieldsrequired" id="contact_phone" value="<?php echo $row_rscontact['contact_phone']); ?>" size="15" (Format: 999-999-9999)'>
                                                    <?php echo->displayFieldHint("contact_phone");?> <?php echo ("class", "contact_phone"); ?>