Public Function cnvCheckUTF8Bytes ( _
    lpInput() As Byte _
) As Long

Long: Zero if the data is invalid UTF-8, or a positive number (1-3) if the input contains valid UTF-8 data.

The return value indicates the nature of the encoded characters:

0 = Not valid UTF-8
1 = Valid UTF-8, all chars are 7-bit ASCII
2 = Valid UTF-8, contains at least one multi-byte character equivalent to 8-bit ANSI
3 = Valid UTF-8, contains at least one multi-byte character that cannot be represented in a single-byte character set