Grid and SubGrid Problems...

I am using dhtmlxSuite_v30_pro_110713_eval. Attached is my app sample transaction screenshot with use of dhtmlx grids all over. my problem is that:

1- if a grid col is of type ‘combo’ which is populated from server, how can I create a new row on TABing or ENTERing at the last grid row so that the new row must have cloned the combo list items as well?
2- how can I save Units grid edited data for the corresponding row cell (Quantity) in selected quantity cell’s user data? Let’s say I want to save the sum of all quantities in units grid rows back on the selected quantity cell on Units grid close and also when the user comes again on that quantity cell he should be able to see the same input data on popped up units grid.