how do I change the image in a CellSelect event in jqgrid?

I am having trouble because in a onCellSelect event of the jqgrid I want to change the image of a cell, for example once I click inside the cell I want to change the image like this:

this is my code for loading the img in the grid:

{display: '', name : '', formatter: image}

function image(cellvalue, options, rowObject){
    if(rowObject[5]== 1){
        return "<span class='ui-icon ui-icon-plusthick'></span>";
    }else{
        return "<span class='ui-icon ui-icon-minusthick'></span>";
    }
}

and my method of

onCellSelect: function() {
    id = $("#list2").getGridParam('selrow'); 
 }, 

how can I archieve that on a onCellSelect change the img of each cell?

I'm not sure I understand correctly, but here's a sample:

onCellSelect: function(rowid, iCol, cellcontent, e) {
   // Get current row content.
   var data = $(this).jqGrid('getRowData', rowid);

   // Edit the column's content. In this case the one named image.
   data.image = "<span class='ui-icon ui-icon-plusthick'></span>";

   // Set the data back.
   $(this).jqGrid('setRowData', rowid, data);
},

I hope it helps.