How to update sales price for already created sales orders by applying latest trade agreements using x++ code

In one of  implementation project. I got a requirement in this Client wants to update sales orders that were created in past.Requirement was to update sales price by applying new trade agreements that were created later in system after the sales order creation.

I used the following code to update the sales price.

private void updateSalesPrice()
{
    SalesLine                   salesLine;
    PriceDiscPolicyCheckPolicy  checkPolicy;
    str                         text;
    SysOperationProgress        operationProgress;
    boolean                     salesLineFound;
    #AviFiles
    // 2013-09-25 #23667_DA0374 dkos: Update Sales Order Unit Price -->
    Dialog                      dialog;
    DialogField                 dfStartDate;
    DialogText                  dialogText;
    TransDate                   startDate;
    // 2013-09-25 #23667_DA0374 dkos: Update Sales Order Unit Price <-- font="">
    ;

    operationProgress = new SysOperationProgress();
    operationProgress.setCaption("@DTD849");
    operationProgress.setAnimation(#AviUpdate);

    // 2013-09-25 #23667_DA0374 dkos: Update Sales Order Unit Price -->
    dialog = new Dialog("@DTD847");
    dfStartDate = dialog.addField(extendedTypeStr(TransDate), "@DTD1042");
    dfStartDate.value(dateNull());

    text = "@DTD845" + '\n\n' +"@DTD846" ;

    dialogText = dialog.addText(text);
    dialogText.displayHeight(4);
    dialogText.displayLengthValue(50);

    if (dialog.run())
    {
        startDate = dfStartDate.value();
    // 2013-09-25 #23667_DA0374 dkos: Update Sales Order Unit Price <-- font="">
        ttsBegin;
        while select forUpdate salesLine
            where salesLine.SalesType   == SalesType::Sales
            &&    salesLine.SalesStatus <=  SalesStatus::Delivered
            &&   !salesLine.InventTransIdReturn //optimisation dkos 2013-09-25
            &&   (salesLine.ShippingDateRequested >= startDate || startDate == dateNull()) // 2013-09-25 #23667_DA0374 dkos: Update Sales Order Unit Price
        {
            salesLine.ManualEntryChangepolicy = 0;                  //optimisation dkos 2013-09-25
            // 2013-02-18 #20169 csek: Job to update SOprice -->
            salesLine.SystemEntryChangePolicy = 0;                  //optimisation dkos 2013-09-25
            // 2013-02-18 #20169 csek: Job to update SOprice <-- font="">

            checkPolicy = PriceDiscPolicyCheckPolicy::newFromParm(salesLine.PriceDiscResultFields::parmPriceDiscResultFields());
            salesLine.salesPurchLine::resetPriceAgreement();
            salesLine.setPriceAgreement(salesLine.inventDim(), null ,false,true);// 2013-02-07 #20169 csek: Job to update SOprice
            salesLine.LineAmount = salesLine.calcLineAmountForced(salesLine.SalesQty, checkPolicy);
            operationProgress.setText(strFmt("@DTD850",salesLine.SalesId));
            salesLine.update();

            salesLineFound = true;
        }
        ttsCommit;
    }
    if (salesLineFound)
    {
        info("@DTD1041"); // 2013-09-25 #23667_DA0374 dkos: Update Sales Order Unit Price
    }
}