■ You have used a character that is not valid in an
  identifier.
 
■ Possible solutions:
 
  • Verify that your DEF FN procedure names contain only
    letters and blanks.
 
  • Verify that your FUNCTION and SUB procedure names start
    with a letter and do not contain these special characters:
         • . (period)    • & (ampersand)     • # (pound)
         • % (percent)   • ! (exclamation)   • $ (dollar)
         • @ (at)        • + (plus)          • - (minus)
 
■ While the FUNCTION procedure names may not contain the
  preceding special characters, they may end with any one of
  these type-declaration characters:
        • @ (at)         • & (ampersand)     • # (pound)
        • % (percent)    • ! (exclamation)   • $ (dollar)
 
■ If you need additional help, move the cursor to a keyword
  and press F1 to open the Help window.