date validations

i would like to validate that my

txtCloseDate is greater than my txt.StartDate

can some one help please.

her is my code

<CODE>

Private Sub img_cal1_Click(ByVal sender As System.Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles img_cal1.Click

Session("Cal1") = True
Session("Cal2") = False

If Me.Calendar1.Visible = True Then
Me.Calendar1.Visible = False
Else
Me.Calendar1.Visible = True
End If


End Sub

Private Sub img_cal2_Click(ByVal sender As System.Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles img_cal2.Click
Session("Cal2") = True
Session("Cal1") = False
Me.Calendar1.Visible = True
End Sub

Private Sub Calendar1_SelectionChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Calendar1.SelectionChanged
If Session("Cal1") = True Then
txt_OpenDate.Text = Calendar1.SelectedDate.ToShortDateString
Session("Cal1") = False
ElseIf Session("Cal2") = True Then
txt_CloseDate.Text = Calendar1.SelectedDate.ToShortDateString
Session("Cal2") = False
End If
Me.Calendar1.Visible = False

End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Me.Calendar1.Visible = True
End Sub

Private Sub txt_CloseDate_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txt_CloseDate.TextChanged

End Sub

</CODE>

if(DateTime.Parse(txtCloseDate.Text) > DateTime.Parse(txtStartDate.Text))
{
// ...do whatever...
}