While this can be done with some effort in VB, you might want to check out two standard products that can do this very effeciently and reliably. Kepware offers Control Logix connectivity. They also offer a toolkit called Client Ace that will give you easy OPC connectivity to VB. There is also a company called Sytech, that offers an excellent product for feeding OPC data into an Excel spreadsheet in a very reliable manor - not keeping Excel open all the time.

Find more information at www.kepware.com and www.sytech.com