Irregular Shaped Forms
I think what you are asking to do is to make an irregular shaped form. Many VB.NET books have a very small section dedicated to this.
Here is a web site that has some sample code that makes an irregular shaped form in the shape of Sponge Bob Squarepants:
http://www.thescarms.com/dotNet/IrregularForm.asp
Another I found is at:
http://www.freevbcode.com/ShowCode.Asp?ID=1124
Hope this helps!