Not in the same way that you can for numeric. However, if you really need to, you could do it using the "advanced features" -- have you ever used a responses.xls file before? If so, you could add the fill in the blank variable name (e.g., let's say "code1") to the list of variables in the responses.xls file. You could pair it with a conditional statement for the skipto value. The conditional statement could check to see if all the characters are letters. If so, then have the skipto value equal "none". Otherwise, have the skipto value equal "code1" -- this will cause MediaLab to stay on this item until the "all letters" condition has been satisfied.