retrieve the cell data to grid to form with another window

I am on middle of something. Please if you any one can help me.
I have one dhtmlx window with form, where on click of a textbox a new window opens where there is a dhtmlxgrid with data. Now what I need is on double click event I want the value of the row to be filled on the textbox. I am short on the knowledge of dhtmlx and json. how could I retrieve the data. It would be very thank full if any expert could help me. thank you

Couldn’t you clarify where you need to retrieve your data from.
You may use the following methods to operate with the values of the cells in the dhtmlxGrid: … t_getvalue … t_setvalue