Checking table has modified in x++

Checking table has modified in x++ :

if(PurchParmLine2.purchQtyCorrection() != 0)
        {     
            ttsBegin;
             purchReceiptEditHistory.clear();
             purchReceiptEditHistory.PurchId = PurchParmLine2.purchTable().PurchId;
             purchReceiptEditHistory.PackingSlipId = VendPackingSlipJour::findRecId(PurchParmTable.VendPackingSlipJour).PackingSlipId;
             purchReceiptEditHistory.ItemId = PurchParmLine2.ItemId;
             purchReceiptEditHistory.InventDimId = PurchParmLine2.InventDimId;
             purchReceiptEditHistory.RefLinesRecId = PurchParmLine2.purchLine().RecId;
             purchReceiptEditHistory.FromQty = PurchParmLine2.PreviousReceiveNow;
             purchReceiptEditHistory.ToQty = PurchParmLine2.ReceiveNow;
             purchReceiptEditHistory.ReceiptCorectionRemark = PurchParmLine2.TIDPurchReceiptCorectionRemark;
             purchReceiptEditHistory.insert();   
            ttscommit;
        }


//BP Deviation Documented
display PurchQty purchQtyCorrection()
{
    return this.PreviousReceiveNow - this.ReceiveNow;
}