Function DerSerie(x As Range, Optional Quoi)
Dim n&, m&, i&, y
On Error Resume Next
If Not IsMissing(Quoi) Then
If Application.WorksheetFunction.CountA(x.Columns(1)) = 0 Then Exit Function
n = Application.WorksheetFunction.Match(String(9, "z"), x.Columns(1), 1)
m = Application.WorksheetFunction.Match(9E+99, x.Columns(1), 1)
If n < m Then n = m
y = x.Columns(1).Cells(n - 1, 1).Value
For i = n To 1 Step -1
If x.Columns(1).Cells(i, 1) <> y Then Exit For
Next i
DerSerie = n - i - (i = n)
Exit Function
Else
DerSerie = ""
If Application.WorksheetFunction.CountA(x.Columns(1)) = 0 Then Exit Function
n = Application.WorksheetFunction.Match(String(9, "z"), x.Columns(1), 1)
m = Application.WorksheetFunction.Match(9E+99, x.Columns(1), 1)
If n < m Then n = m
DerSerie = x.Columns(1).Cells(n, 1).Value
End If
End Function