When populating;
In your populate::aTree routine;
add a field to the TreeQueueType
selected Long ,name('selected | boolean')
Then when populating the queue set this field to true or false.
14.28 required for this next bit;
Later on, after the tree has been populated, You can select something using
p_web.ntTree('aTree','select','rowid')
(In both cases aTree is the Use Equate of the tree field on the form)