[Zope] A tree and a form

Hei, Within a <form> I use a tree that is generated by an sql method already dicussed here on the list. After I opened a branch I want to select different leaves with a <input type=checkbox .. > . Problem is that when you open a branch select some leaves close it and go on to select leaves from another branch you are in troubles. Because when you reopen the branch all buttons are unselected. It's impossible to walk thru the tree, select some leaves and afterwards hit the submit button. So one of the possible solutions is to make the +/- signs submit buttons that save the selected items immediatly in the SQL database. Has anybody any other proposals or some hints were to start ? Wim Vanroose,