That is a composite control.

READ THE SAMPLE CHAPTERS from below books. These ebooks are great much
better than Nikhil and Dye MSPress book and other books. Download controls
from Metabuilders.com and grab the source if he provides it or decompile it
from Remotesoft.com. His lookup /list bound columns is correct way to do
this anyway.

Developing .NET Custom Controls and Designers using VB.NET
www.bluevisionsoftware.com/.../BookInfo.aspx?ID=10

Sample chapters:
www.bluevisionsoftware.com/.../Cha\
pter6.pdf
www.bluevisionsoftware.com/.../Cha\
pter16.pdf

Developing .NET Custom Controls and Designers using C#
www.bluevisionsoftware.com/.../BookInfo.aspx?ID=7

Sample Chapters:
www.bluevisionsoftware.com/.../Sampl\
es/Chapter6.pdf
www.bluevisionsoftware.com/.../Sampl\
es/Chapter16.pdf