[Solved]-Chart highlighting in the highcharts javascript API-Highcharts

Yes it is possible, you can achieve it by catching afterSetExtremes function.

http://jsfiddle.net/JzEnV/

 events:{
                afterSetExtremes:function(){
                    alert(this.min);
                    alert(this.max);
                }
            }

If you would like to get dates, then you can use dateFormat() http://api.highcharts.com/highcharts#Highcharts.dateFormat()