How to only allow alphabets and spaces in the middle in Profile2 field I'd like to only allow alphabets in and spaces in the middle of a my Profile2 "real_Name" field. I have found what I think I need: profile2_form_validate_handler but I don't know how to get it to work.

I think it should be similar to user_validate_name, especially for 

  if (!$name) {
  if (substr($name, 0, 1) == ' ')
  if (substr($name, -1) == ' ')
  if (strpos($name, '  ') !== FALSE)


and I should use 

preg_match('/[^A-Za-z ]/'


I only have a rough idea but I don't know how to make it work and I'd appreciate your help.
I've found the Field validation module that works! I used this regex expression:
^[\x{00c0}-\x{01ff}a-zA-Z0-9]+([- '][\x{00c0}-\x{01ff}a-zA-Z0-9]+)*$

This way I can allow international names and only allow spaces, hyphens and apostrophes in the middle of the name.
It was based on combining

1 https://stackoverflow.com/questions/275160/regex-for-names , and 
2 https://stackoverflow.com/questions/2525327/regex-for-a-za-z0-9-with-dashes-allowed-in-between-but-not-at-the-start-or-e