General :: Setting Monthly Reminder Using Outlook

I'm working on an access database and I need to connect that database to the reminder function of Outlook.

At first, I set the reminder precisely six months before the due date, everything was okay and the reminder worked. But after some revision required by my supervisor, I need to set the reminder based on month (not exactly on the due date), so the tasks which have due dates in the same month will be wrapped into a single reminder. The reminder also should be appear in every two weeks. Here's the code I've been worked on :

Code:
Private Sub Expired_AfterUpdate()
Dim outLookApp As Outlook.Application
Dim outLookTask As Outlook.TaskItem
Set outLookApp = CreateObject("outlook.application")
Set outLookTask = outLookApp.CreateItem(olTaskItem)

[Code]...

I put this code on the AfterUpdate event in the column containing the due date. How should I rearrange the code so it would be able for the reminder to appear based on the month? (just consider that the reminder will be active six months before due date).