Your response is somewhat helpful - but does not completely answer my question. Let me rephrase again for clarity.
What i would like to see, is exactly the 'related grids' demo you have here
but with insertion/edit/delete abilities
on the second (related) grid (Orders). I have no problems with insertion/edit/delete on a single grid.
Now i understand how the SelectedValue property will give me the value i require, however i am not sure how this needs to be used in the codebehind to insert the value into the new 'row'. The third link you provided seems to be in the right area but i have not figured it out yet and time is limited for me ...
Perhaps you can provide me with an example that is simply the related grid demo + insert/edit/delete on the related grid? This would be most appreciated and judging by the moderately high hits on this thread, useful to many others too