how to CHANGE single row IMAGE after data is loaded

there is a convenient way to change single row image (icon) when all data (from external xml, in my case) are loaded.

i see, is possible to view the name of the current image:
obj.getRowTemplate(iRow).getItemTemplate(iCol).getDataProperty("image")
but i need something of "reverse", a kind of
obj.getRowTemplate(iRow).getItemTemplate(iCol).[b]setDataProperty[/b]("image", "newImage")
the getImage function does'n help me:
tableGrid_in.getImage = function(i, j) {
return "someimage";
}
thanks.