Best way to use a form as a GUI, but code it elsewhere - vb.net

Question

I'm wanting to use visual studio to create a form with buttons, but then have it coded elsewhere, so that I can use the events (ie; button clicks) to perform specific actions in this application.
Is it possible/practical to do this? If not/if so, what do I need to look up and learn about from here to be able to implement it? My knowledge base in programming is limitted; I've just been starting to get familiar with Classes.
(I'm working in Autodesk Inventor, and am trying to create a prompt window with buttons to control the output of another program I have. In order to save on the amount of calls/interfacing, I was hoping to just create an uncoded button form, but code it within my program/macro I have within Inventor - its to be a form with six buttons that end up rotating some graphics within the program at a certain stop point, and then the program resumes when the form is closed via the "x")
I have seen posts such as the one below, but that doesn't seem to have the capability to receive user input: How to create a custom MessageBox?
Currently I am here, which works for showing the toolbox. Can someone show me how I would handle the events please?
AddReference "C:\Users\Documents\Visual Studio 2013\Projects\WindowsApplication1\WindowsApplication1\bin\Release\SectionSymToolBox.dll"
Imports System.Windows.Forms
Public Class SectionSymRule
'Public dlg As New System.Windows.Forms.For
Public Shared ToolBox As New SectionSymToolBox.SectionSymToolBox
Dim WithEvents EClass As New EventClass
Sub Main()
ToolBox.Show()
End Sub
End Class
Public Class SectionSymToolBox
Private Sub Main()
End Sub
Public Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
'Swap Symbols
End Sub
Public Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Flip Symbol
End Sub
Public Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
'Flip Text
End Sub
Public Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
'<
End Sub
Public Sub Button5_Click(sender As Object, e As EventArgs) Handles Button5.Click
'>
End Sub
End Class

Answer 1

You can always use Partial Class to split your code into multiple files.
So you create your Form (say Form1) the normal way. Then put the code in another class file with class declared as Partial
For example,
Partial Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
MsgBox(TextBox1.Text)
End Sub
End Class
The other way is to inherit your Form. The inherited form will then have everything of whatever is on the form, with whatever you want to add.
Public Class Form1Code
Inherits Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
MsgBox(TextBox1.Text)
End Sub
End Class