Sub Macro1()
For x = 1 To Sheets.Count
Select Case Sheets(x).Name
Case "synthrjanv", "synthrfev", "synthrmar", "synthravr", "synthrmai", "synthrjuin", "synthrjuil", "synthraout", "synthrsept", "synthroct", "synthrnov", "synthrdec"
Sheets(x).Activate
'ton code...
End Select
Next x