How to create a dialog box in a report

public class ReportRun extends ObjectRun
{
    ItemGroupId itemGroup;
    DialogField dialogItemGroup;
}
public Object dialog(Object _dialog)
{
    DialogRunBase dialog;
    ;
    dialog = super(_dialog);
    dialog.caption("Inventory");
    dialog.addGroup("Item Group");
    dialogItemGroup = dialog.addFieldValue(typeid(ItemGroupId),itemGroup,"Item Group");
    return dialog;
}
public boolean getFromDialog()
{
    ;
    itemGroup   = dialogItemGroup.value();
    return true;
}
public boolean fetch()
{
    Query                   q;
    QueryRun                qr;
    QueryBuildDataSource    qbds;
    QueryBuildRange         qbr;
    ;
    q       = new Query(this);
    qbds    = q.dataSourceTable(tablenum(InventTable));
    qbr     = qbds.addRange(fieldnum(InventTable,ItemGroupId));
    qbr.value(itemgroup);
    qr      = new QueryRun(q);
    while( qr.next() )
    {
        inventTable = qr.get(tablenum(InventTable));
        this.send(inventTable);
    }
    return true;
}

Note: for reference you can check LedgerCheckTrans report