Public Class Form1
 
    Dim cmask As String
    Dim cval As DateTime
    Dim tc As Boolean
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        cval = DateTime.Now
        cmask = "dd.mm.yyyy"
        tb.Text = cval.ToShortDateString()
    End Sub
 
    Private Sub tb_KeyDown(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.KeyEventArgs) Handles tb.KeyDown
        Select Case e.KeyCode
            Case Keys.Up
                UpdateValue(1)
                e.Handled = True
            Case Keys.Down
                UpdateValue(-1)
                e.Handled = True
            Case Keys.Add
                UpdateValue(1)
            Case Keys.Subtract
                UpdateValue(-1)
            Case Keys.Oemplus
                UpdateValue(1)
                e.Handled = True
            Case Keys.OemMinus
                UpdateValue(-1)
                e.Handled = True
        End Select
    End Sub
 
    Private Sub UpdateValue(ByVal v As Integer)
        Dim offset As Integer = tb.SelectionStart
        Dim ss As Integer = offset
        If offset > cmask.Length - 1 Then offset = cmask.Length - 1
        Dim cc As Char = cmask(offset)
        Select Case cc
            Case "d"c
                cval = cval.AddDays(v)
            Case "m"c
                cval = cval.AddMonths(v)
            Case "y"c
                cval = cval.AddYears(v)
        End Select
        tc = True
        tb.Text = cval.ToShortDateString()
        tc = False
        tb.SelectionStart = ss
    End Sub
 
    Private Sub tb_TextChanged(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles tb.TextChanged
        If tc Then Return
        Dim ss As Integer = tb.SelectionStart
        tb.Text = cval.ToShortDateString()
        tb.SelectionStart = ss
    End Sub
 
End Class

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