Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim endCount As Integer = 1000

        Dim finished As Boolean = False

        Dim n1 As Integer = 0 ' 0, 1, 2, 3..
        Dim n2 As Integer = 0 ' 10, 20, 30..
        Dim n3 As Integer = 0 ' 100, 200, 300..
        Dim n4 As Integer = 0 ' 1000, 2000, 3000..

        For I As Integer = 1 To 1000


            While finished = False
                n1 += 1

                If n4 * 1000 + n3 * 100 + n2 * 10 + n1 = endCount Then
                    finished = True
                End If

                If n1 = 10 Then
                    n1 = 0
                    n2 += 1
                    If n2 = 10 Then
                        n2 = 0
                        n3 += 1
                        If n3 = 10 Then
                            n3 = 0
                            n4 += 1
                        End If
                    End If
                End If

                Dim msg As String = n4.ToString() + n3.ToString() + n2.ToString() + n1.ToString()

                TextBox1.Text = TextBox1.Text & vbCrLf & msg
            End While
        Next

    End Sub
End Class