Bindingcontext and determining Position

[CrashDome]

I have a treeview control which lists information based on rows in a datatable (with some as child nodes).

I would like to navigate the position based on the user selected node.

For example:
(Assume a treeview with nodes that are tagged with the PK value)

//POINT A
dataSet.Tables["TABLE"].Rows.Find(treeView.SelectedNode.Tag);
//will find the row in the dataTable...

//POINT B
this.BindingContext[dataSet,"TABLE"].Position = unknownInteger;
//will set the selected row based off an integer index number

now how do I "Find" the index value of where that row is so I can get from POINT A to POINT B??
Is this really simple and I am just missing something?