InfoPath Dev

I followed this tutorial: http://www.bizsupportonline.net/infopath2007/programmatically-add-item-sharepoint-calendar-infopath.htm which works great for what I needed to do. However, while this works well for adding an event to my Sharepoint calendar, I do not know how to manipulate the form that I made from this tutorial to prevent users from adding an event that would overlap with one already in the calendar. From my research, it involves something like event handlers but I am not familiar enough with Sharepoint or InfoPath to make this happen with the specific form that I have created from this tutorial.  If someone could help me, I would greatly appreciate it.

Thank you,
Lauren

I wouldn't know either how to do it using CAML (as used in the article). My first instinct would be to write code that uses the SharePoint Object Model to retrieve all events that might fall in the period specified on the form, and then display a message to the user saying that the specified event overlaps with other events. As you may already know, a calendar is a list in SharePoint, so you can use list SharePoint OM methods on it just like any other SharePoint list. You could also use a SharePoint event handler or workflow (methods 4 and 5 in this post) to do the same thing, but with all of these methods, you'll still have to write code that uses the SharePoint OM to do the check for overlapping events.