Hook ALT key in VSTO Excel Add-in

Question

The solution I need is 99% encapsulated in the accepted solution linked below:

How to perform .Onkey Event in an Excel Add-In created with Visual Studio 2010?

However, it does not seem to work for hooking the ALT key. I have looked around and have come across several C# examples but I am new to programming and I am learning VB .NET so with my level of knowledge I have not been able to port the code in other C# examples successfully to make it work in my VB .NET project.

Since the code linked above already does everything I need, I'd like to keep using it, but I would appreciate it if someone could show me how to make it also hook the ALT key. I suppose there is a constant that needs to be passed and checked for in a specific way but I have not been able to figure it out in the last 4 days since finding this solution. Any help will be much appreciated.

Thanks ever so much!

Edit: @Vincent, here is the code I am testing with that breaks with the overflow error:

Imports InputHelperLib

Public Class ThisAddIn

Dim KeyboardHook As InputHelper.Hooks.LocalKeyboardHook

Private Sub ThisAddIn_Startup() Handles Me.Startup
    KeyboardHook = New InputHelper.Hooks.LocalKeyboardHook
    AddHandler KeyboardHook.KeyDown, AddressOf KeyboardHook_KeyDown
    AddHandler KeyboardHook.KeyUp, AddressOf KeyboardHook_KeyUp
End Sub

Private Sub ThisAddIn_Shutdown() Handles Me.Shutdown
    If KeyboardHook IsNot Nothing Then KeyboardHook.Dispose()
End Sub

Private Sub KeyboardHook_KeyDown(sender As Object, e As InputHelper.Hooks.KeyboardHookEventArgs)
    If e.Modifiers = InputHelper.ModifierKeys.Alt AndAlso e.KeyCode = System.Windows.Forms.Keys.M Then
        System.Windows.Forms.MessageBox.Show("ALT + M was pressed!")
    End If
End Sub

Private Sub KeyboardHook_KeyUp(sender As Object, e As InputHelper.Hooks.KeyboardHookEventArgs)
    If e.Modifiers = InputHelper.ModifierKeys.Alt AndAlso e.KeyCode = System.Windows.Forms.Keys.M Then
        System.Windows.Forms.MessageBox.Show("ALT + M was released!")
    End If
End Sub
End Class

Answer 1

The code in that answer isn't completely valid and doesn't use the best methods of determining modifiers.

Since the standard, low-level keyboard hook didn't work I have added a LocalKeyboardHook to my InputHelper library, which uses the WH_KEYBOARD hook instead of WH_KEYBOARD_LL. The difference is that WH_KEYBOARD requires you to inject a DLL and specify a thread in every process you want to hook. Fortunately, since you're using a VSTO add-in, InputHelper is already loaded into the Excel process along with your add-in.

The compiled DLL can be downloaded in my project's Release section:
https://github.com/Visual-Vincent/InputHelper/releases

(you can also download the InputHelper.vb source file directly from the repository)

Usage example:

Imports InputHelperLib

Public Class ThisAddIn

    Dim KeyboardHook As InputHelper.Hooks.LocalKeyboardHook

    Private Sub ThisAddIn_Startup() Handles Me.Startup
        KeyboardHook = New InputHelper.Hooks.LocalKeyboardHook
        AddHandler KeyboardHook.KeyDown, AddressOf KeyboardHook_KeyDown
        AddHandler KeyboardHook.KeyUp, AddressOf KeyboardHook_KeyUp
    End Sub

    Private Sub ThisAddIn_Shutdown() Handles Me.Shutdown
        If KeyboardHook IsNot Nothing Then KeyboardHook.Dispose()
    End Sub

    Private Sub KeyboardHook_KeyDown(sender As Object, e As InputHelper.Hooks.KeyboardHookEventArgs)
        If e.Modifiers = InputHelper.ModifierKeys.Alt AndAlso e.KeyCode = System.Windows.Forms.Keys.M Then
            System.Windows.Forms.MessageBox.Show("ALT + M was pressed!")
        End If
    End Sub

    Private Sub KeyboardHook_KeyUp(sender As Object, e As InputHelper.Hooks.KeyboardHookEventArgs)
        If e.Modifiers = InputHelper.ModifierKeys.Alt AndAlso e.KeyCode = System.Windows.Forms.Keys.M Then
            System.Windows.Forms.MessageBox.Show("ALT + M was released!")
        End If
    End Sub
End Class