Dim rens As Range
Dim cel As Range
Set rens = Application.Union(Range('C10'), Range('D14'), Range('C20'), Range('G19'), Range('E24'), Range('D26'))
For Each cel In rens
If cel.Value = '' Then
MsgBox 'la cellule ' & cel.Address(False, False) & ' n'est pas renseignée.'
cel.Select
Exit Sub
End If
Next cel