You can write managed code in either C# or VB.NET. To get started review this:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/odc_ip2003_tr/html/odc_INF_Lab_15.asp
If you want to use ActiveX controls, review this:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/odc_ip2003_tr/html/odc_INF_Lab_06.asp
Jason
http://www.k2distillery.com/