Issue with png images in group and "mouseup" detection

[jbv at souslelogo.com]

Hi list,

I have a group containing several fields and 2 images,
and these images are of png format with some transparent
areas.
I need to detect "mouseup" events on these elements with
a "on mouseup" handler in the group script.
When I click on the transparent area of each image,
"mouseup" is detected and the script runs accordingly,
But when I click on the opaque areas of the images, nothing
happens.
I tried to add a "pass mouseup" handler in the script
of each image, but to no avail.
In other words, I am stuck.
Any suggestion ?

Thank you in advance.
jbv