Sub ChoisirLeMois()
Dim x$
x = InputBox("Donner une date dans le mois choisi (j/m/a) :")
If IsDate(x) Then
m = Month(CDate(x)): a = Year(CDate(x))
d = DateSerial(a, m, 0)
For i = 1 To 31
With Worksheets(CStr(i))
If m = Month(d + i) Then .[C1].Value = d + i: .Visible = xlSheetVisible Else .[C1].Value = "": .Visible = xlSheetHidden
End With
Next
End If
End Sub