[Javascript] Changing single click on listboxes to ctrl-click

[Jay Lepore]

Hello,

When a user mouse clicks on a pre-selected listbox, by default, it
unselects everything else I've selected by default.  To change this
behavior I would need the listbox to interpret any click as though it
were a ctrl-click.

Does anyone know of a way to pass that ctrl-click to the element?  

I do not want the user to have to ctrl-click.  I feel a large percentage
of users will single click by mistake the first time.

Thanks.

Jay
www.myinternethandyman.com