Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        TextBox1.TextAlign = HorizontalAlignment.Left
        TextBox1.Text = "Слева"
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        TextBox1.TextAlign = HorizontalAlignment.Right
        TextBox1.Text = "Справа"
    End Sub
End Class