Run-time error '91' Help

[Pookiemeister]

I'm not sure what I am doing wrong here. Sometimes when I open my worbook, I will get a Run-time error '91': Object variable or With block variable not set and sometimes I won't get it. That makes no sense but when I added the Option Explicit to the top of the code I get the error message every time.
When I step through the code, the error occurs after

ActiveWindow.Visible = False

Full Code below:

Option Explicit
Private Sub Workbook_Open()
    
    Dim result As String
    
    ActiveWindow.Visible = False


    result = MsgBox("Do you want to open the product list worksheet prior to opening the userform?", vbYesNo + vbDefaultButton2, "Select Option")
        
    If result = vbYes Then
        Windows("Happy.xlsm").Visible = True
    Else
        selectFilefrm.Show
    End If
End Sub

I'm also not sure if result should be a string and not something else.

Dim result As String

Thank You

 

[Pookiemeister]

Just curious, but let's say it did take a long time to load then what would be your suggestion? Thank you.

 

[Fluff]

You could use Application.Wait to build in a delay, before the code runs. Allowing the workbook to fully open first.