You can hook them by reference with setGridParam 

var grid = jQuery("#jqGridID");

grid.setGridParam({ afterInsertRow: doSomething });

 function doSomething(param1, param2, ...) {

     alert("here");

  }

This by the way will also work in the original grid definition, e.g.

...

afterInsertRow: doSomething,

....

The common way of writing handler code for jqgrid events is to use

anonymous functions, for example,

afterInsertRow : function(rowid,aData)
            {
                jQuery(”#list4″).setCell(rowid, 'note', “<img src = 'add.jpg'>”);
                //alert(”hello”);
            },

How can I use named functions instead of named functions, for example,

afterInsertRow : HandleInsertRow( x, y)

Regards,

Diptendu

PS: 

afterInsertRow : function(rowid,aData) { HandleInsertRow( rowid, aData) }

is NOT a solution for me.