Hi Carlos,

I believe this should work:

([A-Za-z]{4}-[A-Za-z0-9]+)

That will take only letters before the dash (it is set to accept only 4 letters, if it could be less than 4 or more than 4 you can remove the {4} from the expression and put a plus sign instead, like we have at the end.  The part after the dash will take any number of characters, and again if you want it to take a certain number of characters only you can remove the plus sign and put the number of characters you want in the curly brackets (i.e. {6} or {9} for 6 or 9 characters.  Hope this helps!

Rick