This is the third article in the series. The first one focused on the differences between VBA and VSTO, the second Article showed how to migrate a VBA application and obtain functional equivalence on VSTO.
This third article shows you how to maximize the return of the migration by incorporating new .NET features:
http://msdn.microsoft.com/office/default.aspx?pull=/library/en-us/odc_vsto2005_ta/html/OfficeVSTOExcelVBARearchitecture.asp
Enjoy!