Sub TempsDeRetour(TxAct, TxEnr, Invest, EcoInit)
Dim E(1000) As Double
Dim van As Double
Dim cumul As Double
Dim i as integer
van = -1
E(0) = EcoInit
cumul=0
While van < 0
For i = 1 To 1000
E(i) = E(i - 1) * (1 + TxEnr) / (1 + txAct)
cumul = cumul + E(i)
van = cumul - Invest
Next i
Wend
ActiveCell.Value = i
End Sub