You can keep track of your margin values in real time using your TWS Account Window by looking at the Margin Requirements and Available for Trading sections: In Mosaic, click the Account menu option followed by Account Window In Classic TWS, click on the Account icon (looks like a stack of coins) at the top of your TWS.

You can also click the Account menu option and select Account Window.
Please note: Advisors and other multi-client account holders will see a drop-down menu on the Account and Summary tabs to choose either an individual account or an account group.
You can also see how the account's real time margin requirements would change when previewing an opening or a closing order with the Check Margin Impact feature: In the Mosaic Order Entry panel (or any trading tool), click the Advanced icon and then select Check Margin (or Margin/Performance for option orders) From an order line in Classic TWS, use the right-click menu and choose Check Margin Impact.

Additional information on previewing margin requirements can be found in our Users' Guide.