Sub calcul()
Dim Resultat As Double, Ajout As Double
Do
Ajout = Ajout + 0.001
Resultat = Range('qclim') / 1000 * Range('cp') * ((Ajout + Range('dtaspievapo')) - _
Range('tsortieevapo')) + Range('qclim') / (1000) * Range('lv') * ((0.0003 * _
(Ajout + Range('dtaspievapo')) ^ 3 + 0.0065 * (Ajout + Range('dtaspievapo')) ^ 2 + _
0.3005 * (Ajout + Range('dtaspievapo')) + 3.6229) * Range('riat') - (0.0003 * _
Range('tsortieevapo') ^ 3 + 0.0065 * Range('tsortieevapo') ^ 2 + 0.3005 * _
Range('tsortieevapo')) * Range('rse'))
Loop While Resultat < Range('pclim')
Range('iat') = Ajout
End Sub