Sub addColumns()
    Application.ScreenUpdating = False
    With Application.FileDialog(msoFileDialogFilePicker)
        .Title = "Выберите файлы"
        .InitialFileName = ThisWorkbook.Path
        .Filters.Clear
        .Filters.Add "Excel", "*.xls;*.xlsx;*.xlsm", 1: .AllowMultiSelect = True
        If .Show = False Then Exit Sub
        Set mainSh = ThisWorkbook.Sheets(1)
        For i = 1 To .SelectedItems.Count
            Set wb = Workbooks.Open(.SelectedItems(i))
            With wb.Sheets(1)
                j = 1
                Do While mainSh.Cells(1, j) <> ""
                    If .Cells(1, j) <> mainSh.Cells(1, j) Then
                        Columns(j).Insert xlToRight
                        .Cells(1, j) = mainSh.Cells(1, j)
                    End If
                    j = j + 1
                Loop
            End With
            wb.Close True
        Next i
    End With
End Sub