Excel 2010 and checkbox : very slow ?

Hi

I wrote some times ago a macro that add checkboxes in a sheet (I found some part on the net)
On Office 2003 and 2007, no trouble at all. But in office 2010, the same macro is now very slow
here is an example that add a checkbox on 800 rows

Sub Macro1()
Dim l2, i As Integer
Dim r As Range
Dim Data As Range
Dim dtmTest As Date
Dim dtmTest2 As Date

  
    l2 = 800
        
    dtmTest = TimeValue(Now)
    
    i = 0
    Set Data = Range("F3:F" & l2)
    For Each r In Data
        i = i + 1
        Set Cbox = ActiveSheet.CheckBoxes.Add(r.Left + 4, r.Top, r.Width, r.Height)
        With Cbox
           .Value = xlOn
            .LinkedCell = "$G$" & r.Row
            .Display3DShading = True
            .Caption = "ACTIF"
        End With
    Next r
    
    dtmTest2 = TimeValue(Now)
        
    MsgBox (DateDiff("s", dtmTest, dtmTest2))
End Sub

it takes 220 seconds to perform the macro in Excel 2010 and only 17 seconds in Excel 2007 !
If I comment the .value, .LinkedCell and .Display3DShading lines, it only takes 12 secondes in Excel 2010 (but if one of these three lines is present in the code, the macro takes again more than 200 seconds). So it seems this part of the code has a problem ... but I'm unable to find why !

Is there another way to quickly create checkboxes and modify their properties ?

Regards