Assign TVBrange to existent treeitem

Hi, I created a treeitem without tvbrange specified (because by the time of creation I don't know the beginning of tvbrange. Then I start decoding, moving from the end of packet to start direction (this is a feature of that proprietary protocol), adding sub-items to the treeitem, this time with tvbrange. Finally, when all sub-items are decoded and added to the original treeitem, I know total treeitem size and it's beginning. So now I would like to specify tvbrange to the treeitem to make it highlighted when selected. Is there any way to do it?

In developer-guide I can only see treeitem:setlen(), treeitem:settext(), ... but nothing for set beginning of tvb range.