VS 2010 - Post Data To Different Upload Sites

I am creating a program that will assist users upload a file to a couple different upload sites. There will be RapidShare and Uploading. I want to keep the GUI clean and simple, so I do not want to use a web browser. I have not used much Post Data, but am wanting to use it for this job. What I want the program to do is after the user specifies a file, the program will automatically upload the file to the site.

Here is what I have so far:
Public Function MultiUpload(ByRef data As String, ByRef url As String) As String
Dim request As HttpWebRequest = DirectCast(WebRequest.Create(url), HttpWebRequest)
request.Method = "POST"
WebRequest.Create("[URL]")
request.ContentType = "application/x-www-form-urlencoded"
Dim postData As String = data
request.ContentLength = PostData.Length
request.ContentLength = PostData.Length
End Function