How to calculate charge (MarkupTrans) amount from code

static void calculateMarkupTrans(Args _args)
{
    SalesTable              salesTable = SalesTable::find('000854');
    SalesLine               salesLine;
    AmountCur               markupAmount;
    MarkupTrans             markupTrans;
    CurrencyExchangeHelper  curCurrencyExchangeHelper;
    
    while select salesLine
        where salesLine.SalesId == salesTable.SalesId
    {
        while select markupTrans
            where markupTrans.TransTableId  == salesLine.TableId
                &&markupTrans.TransRecId    == salesLine.RecId
        {
            markupAmount = Markup::calcTrans(markupTrans, salesLine.SalesQty, salesLine.LineAmount);
            if (markupTrans.CurrencyCode != salesTable.CurrencyCode)
            {
                // To automatically conver amount Markup::calcMarkupAmount can be used
                curCurrencyExchangeHelper = CurrencyExchangeHelper::newExchangeDate(Ledger::primaryLedger(CompanyInfo::findDataArea(markupTrans.company()).RecId), systemDateGet());
                markupAmount = curCurrencyExchangeHelper.calculateAccountingToTransaction(salesTable.CurrencyCode, markupAmount, true);
            }
        }
    }
}