Hello venkatesh,

Please make sure you have included the required CSS files as well:

<link href="{Path to IG resources}/css/themes/infragistics/infragistics.theme.css" rel="stylesheet" />
<link href="{Path to IG resources}/css/structure/infragistics.css" rel="stylesheet" />

If you need to know when a member is being expanded, you can use the tupleMemberExpanding and tupleMemberExpanded events of the pivot grid:

$("#pivotGrid").igPivotGrid({
    tupleMemberExpanding: function (evt, ui) {
        //return the name of axis, which holds the member and the tuple
        ui.axisName;
        //return a reference to the data source
        ui.dataSource;
        //return the index of the member in the tuple
        ui.memberIndex;
        //return the index of the tuple in the axis
        ui.tupleIndex;
        //return a reference to the igPivotGrid
        ui.owner;
    },
    height: "430px",
    width: "725px"
});

Furthermore this sample shows how to expand members programmatically.

Let me know if you need any further assistance for this matter.

Regards,

Philip