Issues with Checkbox in Header

From searching around the forum I have come up with the following but it has issues. If I do not override the onHeaderClicked the grid sorts on the checkbox column. But if I override onHeaderClicked the checkbox does not update its visual. The onHeaderValueChanged function IS called. I noticed that the visual does update if I sort another column so I tried doing a refresh on the header but that did not work. Any suggestions?

gridObj.setCellTemplate(new AW.Templates.Checkbox, 7);
gridObj.setHeaderTemplate(new AW.Templates.Checkbox, 7);
gridObj.setHeaderValue(false, 7);
gridObj.onHeaderValueChanged =
    function(value, column) {
        alert('c'+column+'='+value);
        return 1;
    }; 
    
var saveDoSort = gridObj.onHeaderClicked;
function myDoSort(event,index,header) {
    if (index == 7) {
       return 1;
    } else {
        if (saveDoSort) saveDoSort(event,index,header);
    }
}

gridObj.onHeaderClicked = myDoSort;