Sub Remplacer()
Dim tablo, resu(), i&
With [A1].CurrentRegion
tablo = .Resize(, 9) 'matrice, plus rapide
ReDim resu(1 To UBound(tablo), 1 To 1)
resu(1, 1) = tablo(1, 3) 'en-tête
For i = 2 To UBound(tablo)
If tablo(i, 9) = "" Then resu(i, 1) = tablo(i, 3) Else resu(i, 1) = tablo(i, 9)
Next
.Cells(1, 3).Resize(UBound(resu)) = resu 'restitution
.Columns(3).AutoFit 'ajustement largeur
End With
End Sub