Standard Letter Variation Regular Expression

Hi:
I am trying to validate a text box through a regular expression validator in asp.net so I am looking for a  regular expression that allows only letters, spaces, hyphen and single quotes but also the Standard Letter Variation such as :
ÃÅÀÂÄáãåàâä... üÝýÿÿ etc.
I have the first part:
^([a-zA-Z '-]+)$  but I dont know how to validate the Standard Letter Variation I showed above.
 
I have  tried with the range for these characters like this:

^([a-zA-Z '- \x192-\x255 ]+)$
Which totally alterates the functionallity of my page!!! the proyect does not recognize the page anymore!!  so I guess asp.net does not support theses ranges. 
I also tried to put all the characters individually. This worked but I realised that with this solution my text box would have to accept numbers, probably because the way you generate these charcters uses numbers ...