Get RowDepth on older Xojo versions to use with InsertRow?

I’m trying to use InsertRow in a hierarchical listbox on 2013r3.3 and this version don’t seem to have RowDepth(row).
How can I get the indent level of the currently selected row to use for InsertRow to insert it with the correct indent?

The selected row here should have been inserted with the same indent as the row above.

Thanks Jean-Paul,
I solved it by reloading the parent folder in the list.
The way I have things in the db I had no possibility of knowing what indent level each folder in the list had.