function iter(rec, listName, cb){
    var lim = rec.getLineCount({sublistId:listName});
    var i = 0;
    var getV = function (fld){
        return rec.getSublistValue({sublistId:listName, fieldId:fld, line:i});
    };
    var setV = function(fld, val){
        rec.setSublistValue({sublistId:listName, fieldId:fld, line:i, value:val});
    };
    for(; i< lim; i++){
        cb(i, getV, setV);
    }
}