How To Add Grand Child Product Using RCOIS AddItem (Doc ID 2623657.1) - more details

Hi as Per above documents we can add a grandchild product when we know the child and parent product details both.

But i have a requirement where i don't know under which grand child will be added?

In our request we have details of Parent product and only the grandchild details( Product Id and Product Name). We need to find the child product details and then add grand child product inside it. How can we find these details at real time( i.e under which child product this product will be added)

/4.Step: Now add the new item

inp.SetProperty("ObjId",head);