I am going through a migration with our credit card processor to a new method using new fields in all of the forms, etc. They used to separate their required credit card expiry fields into MM (card_expiry_month) and YYYY (card_expiry_year) which was fine. I could use dropdowns. NOW they've gone to one field MM-YYYY (card_expiry). How can I put some sort of validation on that field to make sure our customers use MM-YYYY and no slashes, etc.? I put (MM-YYYY) in parens before the input field but people don't read. Any thoughts would be appreciated. Thank you in advance.