Ascii code of text


I would like to know if there is a function to convert text to ascii, and if not what the best way to achiev it.
What I'm trying to do is: see if a ToUpper(character) is between A and Z ascii codes.

Thank in advance,
Pedro Barros
I wasnt very hopefull but

"A" <= ToUpper(character) and ToUpper(character) <= "Z"

seems to do the trick.
You can also do it with a Regex extension, and check for the following regex: "^[A-Z]+$"