How to put a unique id on rows, and retrieve it when selected?

Hi, This is a quetion regarding the GRID

Is there a way of adding a hidden column to the grid, and when selected (onClick) I want to show that value.

Basiclly I wonder how I can retrieve a cell value. I know the column and row.

I got it. I forgot to mention that I used XML. After a bit struggling I found that I could use getData(c,r).