manual sort is not working

I'm trying to run a sort that is not triggered by clicking the column headers. When I run the following code nothing happens to my grid. The direction properties are being assigned accordingly but the final sort method is not taking effect. Any suggestions? Thanks!

function lastsort(){
var dir = obj.getSortProperty("direction");
if(dir!=="ascending") {
dir="ascending"; }
else {
dir="descending"; }
obj.setSortProperty("direction",dir);
obj.sort(0,dir);
}

You have to add at the end

obj.refresh()