You can create and build your own module and then copy the .dll into the bin folder of the Umbraco install. No need to recompile Umbraco itself.
I had a very similar issue, but perhaps with a smaller requirement. I was trying to implement the "last logged in" functionality as described in an Umbraco TV video, to display the last logged in date of members. As the code base has changed, the described method was no longer valid. I found there were 2 general ways to get it to work:
Create your own membership provider. Inherit from UmbracoMembershipProvider and update web config to use your provider. I overrode one method, and my provider code looked like:
using umbraco.BusinessLogic;
using System.Web.Profile;
using System;
namespace zo.Umb.LastLogin
{
public class MyMembershipProvider : umbraco.providers.members.UmbracoMembershipProvider
{
public override bool ValidateUser(string username, string password)
{
var success = base.ValidateUser(username, password);
if (success)
{
var user = GetUser(username, true);
var profile = ProfileBase.Create(user.UserName);
profile["lastLogin"] = DateTime.Now;
profile.Save();
}
return success;
}
}
}
ValidateUser is fired when the user tries to get to secured content.
Note that you now have to update the web.config to point to your custom membership provider.
While this worked, I didn't like moving off of the default provider, editing web.config, etc. and wanted to use the more "standard" approach of the previous version. So I used method 2:
Wire into ApplicationStartupHandler, and subscribe to Member.BeforeSave
using System;
using umbraco.businesslogic;
using umbraco.cms.businesslogic.member;
namespace zo.Umb.LastLogin
{
public class MemberEvent : ApplicationStartupHandler
{
public MemberEvent()
{
Member.BeforeSave += new Member.SaveEventHandler(Member_BeforeSave);
}
void Member_BeforeSave(Member sender, umbraco.cms.businesslogic.SaveEventArgs e)
{
sender.getProperty("lastLogin").Value = DateTime.Now;
}
}
}
If I recall, member.beforesave is not something that's fired when a user is created and saved to the membership store; it's actually fired when a user logs in.