Click Submit Button After String Sent Using HTTPWebRequest?

How can I click the submit button after I've sent a string to a website using httpwebrequest?

Heres my code:
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim wr As HttpWebRequest = DirectCast(WebRequest.Create("[URL]"), HttpWebRequest)
Dim encoder As New System.Text.ASCIIEncoding
Dim stringdata As String = "code=" & Clipboard.GetText & Environment.NewLine & "&submit=submit;"
[Code] .....

But it doesn't work. the string I'm sending converts ok when I open the site + do the conversion manually, but using the above code it reports an error:
Statement fragment: please enter a complete statement.
I've double checked + it must be a problem with the stringdata line.