Option Explicit
Sub InsertFormula()
Dim Plage, Formule$
Application.ScreenUpdating = False
Set Plage = Range("O2:N" & [S65500].End(xlUp).Row) ' Plage utile colonne O
Formule = "=SI($S2='[navette-mac-1.xlsm]Accueil'!$S2;'[navette-mac-1.xlsm]Accueil'!N2;T2)"
Plage.FormulaLocal = Formule ' Collage formule 1
Application.ScreenUpdating = True
Range("N2:O29").Select
Selection.Copy
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
End Sub