Quote from JackR:
Order Ticket Window - Miscellaneous
Use the Miscellaneous order fields to apply order attributes and set specific rules for OCA groups.
NOTE that OCA group names must be unique to ensure proper handling of OCA orders. Once you use a name, you cannot use it again even after the order executes or is canceled.
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To create an OCA order
1.
Display the OCA group field on an order management line:
1.
On the Page menu, click Layout.
2.
In the Columns - Order Row section on the right side of the page, check OCA Group and click OK.
2.
On the TWS screen, create an order (click in the Ask Price to create a BUY order, or the Bid Price to create a Sell order).
3.
Identify the order as part of an OCA group by entering a group name in the OCA Group field (you can use any descriptive name that you want).
4.
Continue to create orders, and identify each as part of the group by entering the same name in the OCA Group field for each order you create.
5.
After you have created all orders for a group, transmit the OCA order by clicking Transmit Page on the Order menu.
NOTE: Because the OCA procedure is an automated process, cannot guarantee that requested cancellations and modifications will reach the specific exchange before an order has been executed.
For a more detailed description of OCA orders and the products and exchanges on which they're available, visit the Order Types information page.