To do what you're trying, only this is needed really, this will open up an excel file so the users can edit it - if this can't be edited, then it's definitley down to the file itself - maybe the read only flag is ticked on the file right click properties? Or maybe there is a piece of code running on the workbook_activate event which is disabling the editing?
Code:
Private Sub Form_Load()
    Dim xclObject As Excel.Application
    Set xclObject = New Excel.Application
    
    With xclObject
        .Workbooks.Open ("c:\temp.xls")
        .Workbooks(1).Worksheets(1).Select
        .Visible = True
    End With
End Sub