.NET bridge for VBA - enables you to use .NET Components in VBA by converting them to regular Win32 DLLs.
It's very simple and convenient SDK.
Search in the Google for ".NET bridge for VBA" to download it.

Main features:
1.Supported interface data types: String, Int32, Int16, Boolean, HBITMAP.
2.Supported interfaces: Properties, Methods with arguments, Events with arguments.
3.Arguments can contain up to 6 Integers and 2 Unicode Strings. (byVal or byRef)
4.Copying the properties with the same type from one control to another.
5.Multilevel inheritance.
e.g: amount = frm1.getIntegerProperty“listBox1”,”Items.Count”)
6.Indexed properties. (get\set)
7.Multiple instances of the same object, they use the same DLL.
8.Saving DLL project with a different name creates a new component.
9.All the string interfaces are Unicode. (supports multiple languages)