Private Shared Function TesteValeur(ByVal Valeur As Double) As Boolean If Valeur = 33.123 Then ' <--- Valeur à trouver Return True Else Return False End If End Function Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click Dim Vect(3) As Double Vect(0) = 12.12 Vect(1) = 15.15 Vect(2) = 33.123 ' <--- Valeur à trouver Vect(3) = 118.118 MsgBox(Array.FindIndex(Vect, AddressOf TesteValeur)) End Sub