VBA function Tách họ và tên (ver 1)

Function Tachhoten(ByVal hovaten As String, n As String) As String
Dim space_left As Integer
Dim space_right As Integer

If hovaten = vbNullString Then GoTo endfunc:
hovaten = Trim(hovaten)
space_left = InStr(hovaten, " ")
space_right = InStrRev(hovaten, " ")
If space_left < 0 Or space_left - 1 < 0 Or space_left + 1 > Len(hovaten) Or space_right < 0 Or _
space_right - 1 < 0 Or space_right + 1 > Len(hovaten) Then GoTo endfunc:

Select Case n
Case "ho"
    Tachhoten = Left(hovaten, space_left - 1)
Case "dem"
    If space_right < space_left + 1 Then GoTo endfunc:
 
    Tachhoten = Mid(hovaten, space_left + 1, space_right - space_left - 1)
 
Case "ten"
    Tachhoten = Mid(hovaten, space_right + 1)
Case Else
    MsgBox ("Chi nhap vao cac gia tri 'ho', 'dem', 'ten'." & vbNewLine & "Hay nhap lai du lieu")
    GoTo endfunc:
     
End Select

endfunc:

End Function