VB.Net button open multiple user and auto login in different window of IE - vb.net

Question

I have a website stored 100 users ....now i want to create a VB form with 100 buttons ....while i click button1, it will open IE then log in users1 automatic and when i click button2 , it will open IE then log in as user2 automatic. user3 until user100 the same ....click from button on vb form.
Note : i am already done to set open IE and log in as different users in each windows but now i am finding how to set auto log in with different users in the same website when i click each button in form.
i have something more about form....i will use ( 100 button click = 100 users = 100 IE window ....)
it depend on user click on button that he need to log in......because we don't know that what button/users/time will he want to click .....
I really need your help urgently...
Thank in advanced.
here is some code of Button_Click
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Using p As New Process
p.StartInfo.FileName = "C:\Program Files\Internet Explorer\iexplore.exe"
p.StartInfo.Arguments = "http://test.com"
p.Start()
End Using

Answer 1

This is the only way I can come up with on how to solve this.
My guess is that your login is using POST variables, it's pretty much standard.
To make this work you would have to allow the username and password to be supplied with GET. That is, sending them in the url like this:
http://test.com/login.php/asp?username=username&password=password
Since you haven't specified whether you use PHP or ASP.NET I will add info on how to get the value for both:
ASP.NET
Request.Querystring("username")
PHP
$_GET["username"];

Answer 2

EDIT based on comment
You are correct it is not possible to isolate separate webbrowser controls.
I would suggest you look into either WaTin to control separate IE instances, or Awsomium .NET, which i believe allows separate sessions in 1.7, though i haven't tested it.
Also be aware that since IE8 session cookies are shared across instanced by default, so you would need to run them with the -nomerge flag. WaTin supports this.
Based on the fact that you have not mentioned this in your question, i am presuming you are using IE7. If that is the case, and this application is not intended to be used on other machines, it should be possible to create a separate application with an embeded webbrowser control, then launch multiple insatances of that application from the main one, so you can add your own communication mechanism, but WaTin is probably a far better idea
OLD ANSWER:
It is very hard to work out what you want to do, but im guessing you want to create a winforms app, that lets you to choose a user account, and then open a browser and login to a website with that account.
Based on that assumption, my suggestion would be to have one button, and some way of selecting the account, say a comboBox, and a webbrowser control:
http://img198.imageshack.us/img198/888/66649645.jpg
Rather than 1 button per user account and trying to manipulate an external browser.
If this is indeed what you want to do, comment and i will edit my answer as required, and provide starting code if you need, but i cant do that without really undertanding what you need to do.