[Help]Destroy Cookie Function error, help

Public Shared Sub DestroyCookie(ByVal CookieName As String)
    Dim CookieObj As HttpCookie = HttpContext.Current.Request.Cookies("CookieName")

    If CookieObj IsNot Nothing Then
        CookieObj.Expires = DateTime.Now.AddDays(-1D)
        HttpContext.Current.Response.Cookies.Add(CookieObj)

    End If
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
     DestroyCookie("xxxxxx.com")

 End Sub

Object reference not set to an instance of an object.