Option Explicit
Sub appliquer_coefficient()
Dim tb, Coeff As Range, i As Integer, j As Integer
Set Coeff = ActiveSheet.Range("A11")
tb = ActiveSheet.Range("A5").CurrentRegion
For i = 1 To UBound(tb, 1)
For j = 1 To UBound(tb, 2)
tb(i, j) = tb(i, j) * Coeff
Next j
Next i
ActiveSheet.Range("A13").Resize(UBound(tb), UBound(tb, 2)) = tb
ActiveSheet.Range("A13").CurrentRegion.NumberFormat = "0.00"
Set Coeff = Nothing
End Sub