[Sada]

Ну как вариант разбить проводку на две

void splitVendTransOpen(VendTrans    _vendTrans)
{
    VendTransOpen       vendTransOpen;
    VendTransOpen       newVendTransOpen;
    ;
    if (this.dutyamount())
    {
        vendTransOpen       = _vendTrans.transOpen(dateNull(), true);
        vendTransOpen.AmountCur = -(taxAmount + this.chargeAmount());
        vendTransOpen.AmountMST = vendTransOpen.AmountCur;
        vendTransOpen.NV_Txt    = this.txtTaxAdminCharge();
        vendTransOpen.doUpdate();

        newVendTransOpen.data(vendTransOpen);
        newVendTransOpen.AmountCur  = -this.dutyamount();
        newVendTransOpen.AmountMST  = newVendTransOpen.AmountCur;
        newVendTransOpen.NV_Txt     = this.txtDuty();
        newVendTransOpen.DueDate    = newVendTransOpen.DueDate + 1;
        newVendTransOpen.doInsert();
    }
}