How to avoid opening grey screens when trying to hide Excel with VBA?

I am trying to make an app that opens a user form at the start, while Excel is being hidden.

The idea is: you open the file, you see the user form without having to see Excel.

When I try to hide the workbook with VBA, it opens empty grey windows. I can only close these windows in Task Manager.

Why does this happen and how can I fix it?

I tried this code in the ThisWorkbook module in the VBA editor:

Private Sub Workbook_Activate()
    Application.Visible = False
    UserForm1.Show
End Sub

It hides the main Excel screen, but shows grey windows.

Instead of ThisWorkbook I put this code in a module:

Sub Auto_open()
    UserForm1.Show
End Sub

It also opens the grey windows.

I think the answer is not to try to hide the app, but to move it out of view. Try this code:

Option Explicit


Private myWindow As Window

Public Sub showForm()
    UserForm1.Show
    
    Set myWindow = Application.Windows(1)
    myWindow.WindowState = xlNormal

    '// move the window out of view here
    myWindow.Top = -1000
    UserForm1.Top = 50
    UserForm1.Left = 50
    
End Sub

Public Sub hideForm()

    myWindow.Top = 100
    myWindow.WindowState = xlNormal
    Unload UserForm1
    
End Sub