Soft Loading Grid Data

I am trying to load a grid with 1000 rows of 18 columns. To avoid the initial page load delay of downloading that much data, I tried to use a function to load the data. If the full 1000 rows of data was not available, then the grid would not display, even though I was loading the grid from:
inventory.setCellText(function(col, row) { return gridData[row][col]; } );
So I set the roecount to 20 (the initial array size) and made a function that loads the data in the background sets the row count and calls refresh:
inventory.setRowCount(gridData.length);
inventory.refresh();
If I do not move off the first displayed rows it looks normal, if I start scrolling then the grid jumps as the refresh is called and my selection is lost. Is there a method I should be calling instead of refresh as I add data to the array?

Thanks.