Hi,
1. I did this work some time ago and posted the example here. But actually I don't remember when. It uses "Microsoft TreeView Control ver.5.0." If you have another version you may need to reload control into ActiveX container. But in any case you will find the idea of how to Add and Remove items into/from different levels of tree. This VI is made under LV 6.0.
yuo can download it from here:
treeview.vi2.And as far as I know tree control exists in LV7. So change the version and you'll get the easy way to work with them.
Good luck.
Oleg Chtuko.