fires when the width of a column was changed
| id | string | the id of the column |
| newWidth | number | the new width set for the column |
| oldWidth | number | the previous width of the column |
| user_action | boolean | true if the column was resized by a user action |
$$("table").attachEvent("onColumnResize",
function(id,newWidth,oldWidth,user_action){
alert("New column width: " + this.getColumnConfig(id).width );
});