I have a single line text control in an item form and I'm having trouble with the exact validation settings to produce the desired result. I'm new to regex but I've managed to at least set validations to allow all alphanumeric characters and just the dash ( - ) special character. However, what I would really like is to only allow specific two-letter combinations (i.e. NW, SU), two-digit numbers (1-99) and the dash ( - ) special character. I've attempted many permutations in regex (scouring the web and these forums for clues) but have had no luck so far. Any help would be much appreciated and thanks!