I think I found out...
'here your matter: you did not refer workbook to setted excel variable!
Set objExcelWkBk = objExcelApp.Workbooks.Open(App.Path & "\boom.xls")

'instead of
'set objExcelWkBk = Excel.Workbooks.Open(App.Path & "\bom.xls")
' and on closing:
'workbook is not nothing
If Not objExcelWkBk Is Nothing Then
Set objExcelWkBk = Nothing
End If

If Not objExcelApp Is Nothing Then
'excel is not quitted!
objExcelApp.Quit
Set objExcelApp = Nothing
End If


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