Prevent Excel From Maximizing When UserForm Is Active

[Excel Fox]

Instead of preventing Excel from maximizing, why don't you simply make the application invisible, whenever your form is open? Here's a sample. Post back if this is not what you needed.

I've just added a few lines to check the visibility toggle, by simply clicking on the userform. But this code you can remove, and is not required for what you were looking for.

Code in user-form

Option Explicit
Dim bln As Boolean

Private Sub UserForm_Activate()
    
    Application.Visible = False
    bln = True
    
End Sub

Private Sub UserForm_Click()

    Application.Visible = bln
    bln = Not Application.Visible
    
End Sub

Private Sub UserForm_Terminate()

    Application.Visible = True

End Sub

Code in Workbook module (to activate the form immediately )

Option Explicit

Private Sub Workbook_Open()

    frmTest.Show
    
End Sub