"within graphic" question

[jbv at souslelogo.com]

Hi list,

I have a graphic made of a list of points. This graphic is opaque
and invisible, its filled property is set to true (according to
the doc).
In my card script I have something like :
on mousedown
   put within(grc "mygraphic", the clickloc)
end mousedown

but it always returns false, even when I click
inside the clickable area of the graphic...
What am I missing ?

Thanks in advance.
jbv