ok here is the sample code..
i m using DateTime Picker instead of textbox.
private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
{
label1.Text = dateTimePicker1.Value.ToShortDateString();
label2.Text = dateTimePicker1.Value.AddDays(1).ToShortDateString();
label3.Text=dateTimePicker1.Value.AddDays(2).ToShortDateString();
}