Using SPLongOperation Within ItemUpdating Event Receiver

I have an event receiver triggered on ItemUpdating that may take some time to run. The code is as follows:

using (SPLongOperation longOperation = new SPLongOperation())
                            {
                                //Custom Messages on the Spinning Wheel Screen
                                longOperation.LeadingHTML = "Enumerating ...";
                                longOperation.TrailingHTML = "Please wait while the related items are checked.";

                                //Start the long operation
                                longOperation.Begin();

                                foreach (SPListItem someItem in items)
                                {

                                    strNCStatus = ncItem["Status"].ToString();

                                    if (strStatus != "Closed")
                                    {
                                        properties.ErrorMessage = "The Status Of The Item Cannot Be Changed To Closed Because There Are Open Related Items.";
                                        properties.Status = SPEventReceiverStatus.CancelWithError;
                                        properties.Cancel = true;
                                    }
                                }

                                //End the long operation
                                string redirectURL = SPContext.Current.Web.Url;
                                longOperation.End(redirectURL);
                            }

You will notice from the code that SPLongOperation(this.Page) is not calling the this.Page part.

I want the processing page to display while this operation takes place in the ItemUpdating.

I don't have a reference to this.Page because my code is running on ItemUpdating event receiver.

Is it valid to use SPLongOperation within ItemUpdating and if so how can I use SPLongOperation without using this.Page as the parameter?