La voilà la solution
Sub copieformule()
With Sheets("data")
Set premier = .Cells(2, 3)
n = 0
While premier.Offset(n, 0) <> ""
Set lformule = Sheets("formula").Columns(2).Find(premier.Offset(n, 0))
If Not lformule Is Nothing Then
If lformule.Offset(0, 9).HasArray Then
premier.Offset(n, 9).FormulaArray = lformule.Offset(0, 9).FormulaR1C1
Else
premier.Offset(n, 9).Formula = lformule.Offset(0, 9).FormulaR1C1
End If
Else
premier.Offset(n, 9) = ""
End If
n = n + 1
Wend