I don't understand if you need a client/server, in terms of Networking application..or..(considering you wrote "Keylogger") you need an application that generates a "Server"..Stub.
In the first case i suggest you to look into using a TcpClient..Serialization..Delegates..and stuff like that.
In the second case, you need to write your stub with all the functions you need, next you can activate your function by a config file appending it to your Stub (basic way) or manipulate variables and generate your stub directly from is source by using Codedom.
Let's say you are going to use settings with one option only, imagine you have in your Builder a checkbox to select if your Stub will have yuor option activated or not, ...and a button to generate your Stub.
Code
Private Sub GenerateServerButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GenerateServerButton.Click
Dim splitter as strig = "splitter"
Dim settings As String = ""
if optioncheckboxes.checked = true then settings &= "True" & splitter else settings &= "False"
IO.File.AppendAllText(you stub path*, settings)
*your stub path could came from a savefilefialog, or a file extracted from your builder resorces, or a specific file
Now, in your stub in the main Sub you can read settings as this:
Code
dim splitter as string = "splitter"
Try
Dim data As String = IO.File.ReadAllText(Application.ExecutablePath)
Dim settings() As String = Split(data, splitter)
Dim optionactivated as string = settings(1)
If optionactivated = "True" then
yourfunction()
end if
catch
end try
This is the very basic way to go..there could be some error in my example, i wrote it fast, but i hope it will give you a good start.