Salut iliess,
à tester car, à l'aveugle...
Private Sub Test()
'
Dim tTab,i&
'
With Worksheets("Grand Livre")
tTab = .Range("F3:K" & .Range("A" & Rows.Count).End(xlUp).Row).Value
For i = 1 To UBound(tTab, 1)
If Left(tTab(i, 1), 21) = "Piece Encaissement / " Then _
tTab(i, 6) = Format(Left(Right(tTab(i, 1), 12), 10), "mm/dd/yyyy")
If Left(tTab(i, 1), 21) = "PIECE Synthese GTR-SI" Then _
tTab(i, 6) = Format(Mid(tTab(i, 1), 44, 10), "mm/dd/yyyy")
If Left(tTab(i, 1), 21) = "Piece journée encaiss" Then _
tTab(i, 6) = CDate(Replace(Right(tTab(i, 1), 10), ".", "/"))
Next
.Range("F3").Resize(UBound(tTab, 1), 6).FormulaLocal = tTab
End With
'
End Sub
A+