[Solved]-Execute function after zoom highcharts-Highcharts

use the aftersetextremes event:

    xaxis: {
        categories: ['jan', 'feb', 'mar', 'apr', 'may', 'jun',
            'jul', 'aug', 'sep', 'oct', 'nov', 'dec'],
        events: {
            aftersetextremes: function(event){
                if (this.getextremes().datamin < event.min)
                    alert("zoomed in!");
            }
        }
    }

here's a working example: http://jsfiddle.net/rcdfw/