Sending ICalendar event to client while still continue running your code

I have built a basic calendar event using DDay.iCal, when I click "Add to calendar" link I produce an event and then sends this to the client.

Basically, my application works like this.

1. A User logs in.
2. Selects a specific date.
3. Books a specific timeslot
4. Clicks the "Add to calendar" link

Sending the event is done by using Response.Write() which sends the following to the client:

Response.ContentType = "text/calendar";
Response.AddHeader("Content-disposition", "attachment; filename=appointment.ics");
Response.Write(iCalString);

The above works fins but it requires me to first book the event then manually and then click the "Add to calendar" link.

I want to merge the steps 3 and 4. But when trying to do so the event booking gets saved to the database but the screen does not get refreshed.

Is there a "simple" way to get around this?