VERIFICAR SE A HORA E VALIDA

Private Sub Command1_Click()
    MsgBox IsDate("23:59")
    MsgBox IsDate("24:59")
End Sub

'Adicione um TextBox com o nome de txtHora e use este código.
Private bDozeHoras As Boolean
Private bComSegundos As Boolean

Private Sub txthora_Change()
    With txthora
         If bDozeHoras Then
             If Len(.Text) = 1 And .Text > "1" Then .Text = "": .SelStart = Len(.Text)
             If Len(.Text) = 2 And Mid(.Text, 2, 1) > "2" Then .Text = Left(.Text, 1): .SelStart = Len(.Text)
         Else
             If Len(.Text) = 1 And .Text > "2" Then .Text = "": .SelStart = Len(.Text)
         End If
        
         If Len(.Text) = 2 And Mid(.Text, 1, 1) = "2" And Mid(.Text, 2, 1) > "4" Then .Text = Left(.Text, 1): .SelStart = Len(.Text)
        
         If Len(.Text) = 4 And Mid(.Text, 4, 1) > "5" Then .Text = Left(.Text, 3): .SelStart = Len(.Text)
        
         If bComSegundos Then
             If Len(.Text) = 7 And Mid(.Text, 7, 1) > "5" Then .Text = Left(.Text, 6): .SelStart = Len(.Text)
         End If
        
         Me.Caption = Len(.Text)
   End With
End Sub

Private Sub txthora_GotFocus()
   If bComSegundos Then
       txthora.MaxLength = 8
   Else
       txthora.MaxLength = 5
   End If
  
   Screen.ActiveControl.SelStart = 0: Screen.ActiveControl.SelLength = Len(Screen.ActiveControl.Text)
End Sub

Private Sub txthora_KeyPress(KeyAscii As Integer)
   If KeyAscii = 13 Or KeyAscii = 8 Then
       If Len(txthora.Text) = 4 Then txthora.Text = Left(txthora.Text, 3): txthora.SelStart = Len(txthora.Text)
       If Len(txthora.Text) = 7 Then txthora.Text = Left(txthora.Text, 6): txthora.SelStart = Len(txthora.Text)
   Else
       If Not IsNumeric(Chr(KeyAscii)) Then
           KeyAscii = 0
       Else
           If Len(txthora.Text) = 2 Then txthora.Text = txthora.Text & ":": txthora.SelStart = Len(txthora.Text)
           If bComSegundos Then
               If Len(txthora.Text) = 5 Then txthora.Text = txthora.Text & ":": txthora.SelStart = Len(txthora.Text)
           End If
       End If
   End If
End Sub

Private Sub txthora_LostFocus()
   With txthora
      If bComSegundos Then
         If Mid(.Text, 3, 1) <> ":" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
         If Mid(.Text, 6, 1) <> ":" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
        
         If bDozeHoras Then
             If Left(.Text, 1) > "1" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
             If Left(.Text, 2) > "2" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
             If Mid(.Text, 4, 1) > "5" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
             If Mid(.Text, 7, 1) > "5" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
         Else
             If Left(.Text, 1) > "2" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
             If Mid(.Text, 4, 1) > "5" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
             If Mid(.Text, 7, 1) > "5" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
         End If
      Else
         If Mid(.Text, 3, 1) <> ":" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
        
         If bDozeHoras Then
             If Left(.Text, 1) > "1" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
             If Left(.Text, 2) > "2" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
             If Mid(.Text, 4, 1) > "5" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
         Else
             If Left(.Text, 1) > "2" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
             If Mid(.Text, 4, 1) > "5" Then: MsgBox "Hora inválida!": .SetFocus: Exit Sub
         End If
      End If
   End With
End Sub

'Obs:
'1 ) A hora esta no formanto "HH:MM" para se usar no formato "HH:MM:SS" ative a variável : bComSegundos
'2) A hora esta no formato de 24 horas, para se ativar o formato de 12 horas, ative a variável : bDozeHoras