What is internalid of Select on ItemFulfillment record?

This week I was working on Itemfulfillment Record after many months and I need logic where those lines which are checked comes in calculation.

This is possible when order is partially fulfilled.
So I need Internalid of Fulfill checkbox to check which is checked and which is not.
Internal id of Fulfull Line Item checkbox is {itemreceive}

How to Use this?

Example:
var iFRecord = nlapiLoadRecord('itemfulfillment', fulfillmentid);
                var iflinecount = iFRecord.getLineItemCount('item');
                if(iflinecount)
                {
                    for(var ab=1; ab <= iflinecount; ab++)
                    {
                        var ifitem = iFRecord.getLineItemValue('item','item',ab);
                        var itemreceive = iFRecord.getLineItemValue('item','itemreceive',ab);
                        if(itemreceive == 'T')
                        {
                            //add your logic here
                        }
                    }
                }

Above is Example in Case of Load as script was on After Submit. User can change it to create also as per their need.