VBA script for checkbox not working

I have a problem in Excel 2013. Yesterday I put the following code in Excel by rightclicking the tab of my worksheet (Alt-F11) :

Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
If Not Intersect(Target, Range("D3:T42")) Is Nothing Then
Application.EnableEvents = False
If Target.Value = ChrW(&H2713) Then
    Target.ClearContents
    Cancel = True
Else
    Target.Value = ChrW(&H2713)
    Cancel = True
End If
End If
    Application.EnableEvents = True
End Sub

This code is supposed to add a checkmark in the defined cells after double clicking. While this code worked fine yesterday, it now does not work anymore. I have tried everything but just do not get it to work. Any ideas ?

PS I would like to use such a code since a sheet with many form checkboxes makes it very slow (at least in my case)

Regards, Arno