Private Sub Worksheet_Change(ByVal Target As Range)
Dim tablo, i As Long, t
tablo = [c3:c500]
For i = 1 To UBound(tablo)
t = tablo(i, 1)
If Not (IsEmpty(t) Or IsError(t)) Then _
If IsNumeric(Replace(t, ".", ",")) _
Or IsNumeric(Replace(t, ",", ".")) _
Then tablo(i, 1) = Val(Replace(t, ",", "."))
Next
[c3:c500] = tablo
End Sub