Sub Add_DIFF()
Dim a As Worksheet, b As Worksheet, i&, dm As Range
Set a = Sheets("NEW")
Set b = Sheets("OLD")
Set dm = b.Range(b.Cells(2, 3), b.Cells(Rows.Count, 3).End(3))
Sheets("DIFF").Range("A1:C1") = Array("Ticket", "Date ouverture", "Date modification")
For i = 2 To a.Cells(Rows.Count, 3).End(3).Row
If IsNumeric(Application.Match(a.Cells(i, 3), [dm], 0)) Then
Sheets("DIFF").Cells(Rows.Count, 1).End(3)(2).Resize(, 3).Value = a.Cells(i, 1).Resize(, 3).Value
End If
Next
End Sub