How to program in VB.NET for the first time
You may not be using Modbus protocol. You may not be using CRC-16. You may not be using VB.NET. However, if
you're looking for a quick way to wrap your mind around cyclic redundancy check and error derection
algorithms, you should find the VB.NET source code presented on this page quite useful:

http://vbnetforest.wordpress.com/2011/07/28/my-first-modbus-crc-program-in-vb-net/

In case if you don't have a way to take note, try to remember this: VBNETFOREST.com go there then click on LESSONS.