//=== There are a series of articles explaining COM Shim :
Part1 : COM Shim Background / Installation / Startup example
The Visual Studio Tools for Office(VSTO) loader is an unmanaged DLL that acts as a shim to load the .NET CLR and then your custom managed assembly.
A custom COM shim has exactly the same behavior.
If you use the VSTO loader, you can set Office macro security to High (or Very High in Office 2003), because a managed smart tag loaded by the VSTO loader is not subject to Office macro security checking at all.
Part2 : ComShimWizard for VS2010
Part3 : How to get a working 32-bit shim wizard to work with 64-bit of Office
//=== COMShim Wizard download
COMShim Wizard for Office2007 + VS2008/VS2005
Older version download
COMShim Wizard for Office2003