Option Explicit
Public maCellule As Range
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Excel.Range, Cancel As Boolean)
Cancel = True
If Not Application.Intersect(Target, Range("A6:AG37")) Is Nothing Then
Set maCellule = Cells(Target.Row, 1 + 3 * Int((Target.Column - 1) / 3))
MsgBox maCellule 'juste pour le test
If IsDate(maCellule) Then Userform1.Show
End If
End Sub