Got some work to do at home from college... Totally a noob with VB so please forgive me :)

But, basically,
Code:
[U]Private Sub[/U] RadioButton1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
        txtEvent.Text = "Tennis"
        cyclingradio.Visible = True
        swimmingradio.Visible = False
        tennisradio.Visible = False
...