Yikes on the thumb....
Firstly, I want it to be known clearly that you are NOT using Visual Basic.... the used the same name, but it's actually .NET or express, but not legacy VB. The Forum that you are posting in, is for Visual Basic from 6 and below.... you are using .NET.
Your question, however, is related more to the concept of programming than to a specific language, so I'm not going to move the thread. I don't remember exactly if .NET's textboxes use the .text property, or the .value property, but I'll post code for both. One problem that you are going to face is the fact that the script file, IS NOT part of your program, which means you will either have to pass it parameters, OR you'll have to set an option somewhere that the script reads when it runs.
The two ways are basically like this, to pass the parameter:
you would set the vbscript file up to read whatever is passed it on the command line, just like if you click start, go to run, and type in: notepad hello.txt you'll see notepad do something out of the ordinary.... if hello.txt does not exist, notepad will ask you if you want to create a new file. You can make your VBScript program take parameters also, so you could call it with something like:
myscript.vbs jerry
and then it would use jerry as the input to display in the echo command.
The other method, would be to have the VB.Net Program write a value somewhere, like in a file, or in the registry, and then make the script program actually read that value from the file or registry, and act accordingly....