Filter Query Form DataSource using DynaLink

example code on form VendPurchaseOrderJournal , datasource VendPurchOrderJournal method init()

public void init()
{
    QueryBuildDataSource  queryDataSourceLink;
    super();

    if (element.args().dataset() == tablenum(PurchReqLine))
    {
        this.query().dataSourceTable(tablenum(VendPurchOrderJour)).clearDynalinks();

        queryDataSourceLink = this.query().dataSourceName(identifierstr(VendPurchOrderJour));
        queryDataSourceLink.relations(true);
        queryDataSourceLink.addDynalink(fieldnum(VendPurchOrderJour, PurchId),
                                        element.args().record(),
                                        fieldnum(PurchReqLine, PurchId));
    }

    //add by fanddy , for inqueries confirm PO
    if (element.args().dataset() == tablenum(TECPOGroupHeader))
    {
        this.query().dataSourceTable(tablenum(VendPurchOrderJour)).clearDynalinks();

        queryDataSourceLink = this.query().dataSourceName(identifierstr(VendPurchOrderJour));
        queryDataSourceLink.relations(true);
        queryDataSourceLink.addDynalink(fieldnum(VendPurchOrderJour, TIDPOGroupId),
                                        element.args().record(),
                                        fieldnum(TECPOGroupHeader, POGroupId));
    }
    //END
}