There is no part of the TurboTax software called the "Refund Planner." What are you trying to do?
To plan for next year?
There is one thing you can do in your current online return. You can go though the Estimated Tax section which will prepare estimated payments for next year. That may help you calculate what you might owe. You can just type W4 in the search box at the top of your return , click on Find. Then Click on Jump To and it will take you to the estimated tax payments section. Say no to changing your W-4 and the next screen will start the estimated taxes section. You can do something similar for state by preparing state estimates. You have to go though the state tax tab and towards the very end of the state interview it will ask if you want to prepare estimates.
OR go to
Federal Taxes or Personal (H&B version)
Other Tax Situations
Other Tax Forms
Form W-4 and Estimated Taxes - Click the Start or Update button
To get back into your return, try this, you can sign back onto your account, and click on Add a State. This should get you back into your return. But be very careful not to change anything in your real filed return.
Or If you are using the Desktop Software there is a What-if worksheet.