CMS Made Simple Forums

I have created a new content type as a module. The new content type is just an extension of the regular "Conntent" content type with a few extra fields in it. Now to the problem: How do I create an event handler to save these extra fields? I guess I would have to use the "ContentEditPost" event, but how do I set this up (preferably to call a "SaveExtendedContent" function to save the extra fields inside my contenttype.extendedcontent.php in the module directory)?