Function Exist_Rep(Rep As String) As Boolean
On Error Resume Next
Exist_Rep = GetAttr(Rep) And vbDirectory
End Function
Sub Dossier()
Dim Chemin, Nom, Dossier As String
Chemin = Range("A1")
Nom = Range("B1")
Dossier = Chemin & Nom
If Not Exist_Rep(Dossier) Then MkDir Dossier
End Sub