Sub Si()
Dim R As Range
Set R = Range("C12:D13,I10:i12,I6,K6,M6,I25:I27").Find("")
If Not R Is Nothing Or [I21] & [I22] = "" Then _
MsgBox "pas d'accord pour continuer", vbCritical, "Conditions non requises": Exit Sub
MsgBox "une minute, je vais faire impression !", vbInformation, "Pour la suite..."
End Sub