Help with a dojo table (setStore)

I am looking for someone with dojo knowledge that can help me dynamically update a dojo table through the setStore call. I have a dojo table. It is working fine. I need to dynamically update the dojo table. I am able to use ajax to dynamically update the table - the ajax/dynamic part works fine. I am able to create a new ItemFileReadStore that contains the data - works fine. Next, I try the code: var grid = [login to view URL]("grid"); and I can't find the grid. The grid variable is null. The next line in the code is [login to view URL](newStore); but grid is null so this doesn't work. I am looking for help on a dojo table. I am not understanding why this line is returning null. var grid = [login to view URL]("grid");