Retrieving data from grid

I am trying to retrieve data from the grid but I cant seem to figure out how to retrieve it. I try obj.getValue(0, 0) with the examples and all i ever get is obj.getValue is not a function.
I am tring to find a way for the user to select the rows he wants and then I want to take the information and send it in a form to another page to have it removed from a database. But I cant even seem to get any information from teh grid. Any help is appreciated