CPOS (string, substring)
CPOS (string, substring, n)

   Synopsis:
      Returns the position in the string of the first occurence of any character
         from the substring

   Notes:
      (Axbasic labels the first character in the string as 1, the second as 2,
         and so on.)
      If none of the characters in the substring occur in the string, 0 is
         returned. If either the string or the substring are empty strings, 0 is
         returned.
      If the third argument is specified, the search begins at the nth character
         in the string and proceeds to the right. CPOS(string, substring, 1) is
         interchangeable with CPOS(string, substring).
      If n is not an integer, it is rounded off. An error occurs if n is zero
         or a negative number.
