Read A Packet Of Data Which Has Come In From RS232

I am trying to read a packet of data which has come in from RS232. I need to be monitoring the port until data comes in to be actioned. I have been doing this fine for some time using the following code:

Dim strline As String = Nothing
Dim comPort As SerialPort
Dim bIsOpen As Boolean = False

[Code]....

The code above works without a problem unles byte 1 or two are greater than 127. Basically, all of the characters that are not converted seem to be 128-255.

I am using VB 2008 express. Clearly I need to read each byte individually and store it as a byte within an array instead of a string but i am not sure how to do this.

how to get around this either through reading bytes properly or through using a different encoding format