Private Sub NumericUpDown1_ValueChanged _
  (ByVal sender As System.Object, ByVal e As System.EventArgs) _
  Handles NumericUpDown1.ValueChanged
 
  With MaskedTextBox1
     Dim tbval As Integer = CInt(NumericUpDown1.Value)
     .Text = Format(tbval \ 60, "00 ") + Format(tbval Mod 60, "00")
  End With
End Sub
 
Private Sub MaskedTextBox1_KeyDown(ByVal sender As Object, _
        ByVal e As System.Windows.Forms.KeyEventArgs) _
        Handles MaskedTextBox1.KeyDown
 
     Dim t As String = MaskedTextBox1.Text.Trim
     Dim h, m As Integer
     If e.KeyCode = Keys.Enter Then
        If t.Length > 1 Then h = CInt(t.Substring(0, 2))
        If t.Length > 3 Then m = CInt(t.Substring(3, 1))
        If t.Length > 4 Then m = CInt(t.Substring(3, 2))
        If m > 59 Then m = 59
        NumericUpDown1.Value = h * 60 + m
     End If
End Sub