Starting a process

Hi,
I have a third party prog. that I need to use. This program communicates with a device through a serial port. This device is a digital pressure gauge and after measuring preasure it outputs a file and then my VB app will read this file. When I use Diagnostics.Process.Start the app starts but i dont get any output from it.

Now I have COM prot 2 on my machine and it is also set to COM port 2 in the third party App. but for some reason when I use System.Diagnostics.Process to start the App I get a message that the COM is not set correctly so I am trying to find some code for VB.NET to set the COM port before opening the program. If you have any idea how to do this Id like the help.
Thank you