Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = 0
'при любых изменениях размеров образцов "Площадь образца ="
If Not Intersect(Target, Range("A6:C9")) Is Nothing Then
    With Range("E6:E9")
        .FormulaR1C1 = _
            "=ROUND(RC[-4]*RC[-2]/100,0)"
        .Value = .Value
    End With
    Application.EnableEvents = 1
    End If
Application.EnableEvents = 1
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
    If Not Intersect(Target, Range("A6:D9")) Is Nothing Then
        Application.EnableEvents = 0
        With Range("E6:E9")
            .FormulaR1C1 = "=ROUND(RC[-4]*RC[-2]/100,0)"
            .Value = .Value
        End With
        Application.EnableEvents = 1
    End If
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim ar As Range, arr As Variant
    On Error Resume Next
    'при любых изменениях размеров образцов "Площадь образца ="
    With Me.UsedRange.Columns("A:D")
        For Each ar In Intersect(.Offset(5), .Cells, Target).Areas
            With ar.Offset(, .Column - ar.Column).Resize(, 5)
                arr = .Value
                For i = 1 To .Rows.Count
                    arr(i, 5) = Round(arr(i, 1) * arr(i, 3) / 100, 0)
                Next
                Application.EnableEvents = 0
                .Value = arr
                Application.EnableEvents = 1
            End With
        Next
    End With
End Sub

If Not Intersect(Target, Range("A6:D9")) Is Nothing Then

If Target.Address = "A6:C9" Then

Application.EnableEvents = 1