I wish to do the same thing. I had the following code:

colModel: [
{ name: 'ID', width: “100”, sortable: true, sorttype: 'int', key: true },
{ name: 'FirstName', width: “150”, sortable: true, sorttype: 'text', stype: “select”, searchoptions: { value: function (pdata) { getFilterData(pdata); } } },
{ name: 'LastName', width: “150”, sortable: true, sorttype: 'text', search: false}]

However it never seems to call the function I try to call.