With UDF (Excel <2003)


Function sumVisibles(champ As Range)
Application.Volatile
t = 0
For Each c In champ
If c.EntireColumn.Hidden = False Then t = t + c.Value
Next c
sumVisibles = t
End Function


Private Sub Worksheet_SelectionChange(ByVal Target As Range)
calcultate
End Sub

Cordialy JB