Hi,
To add the conditional formatting for a button, follow the below steps.
1. Double click on button. You will see Button Properties window.
2. Go to Display tab. Click on conditional formatting button.
3. Then click Add.
4. Select ‘Issubmitted' field in the first drop down. Is not equal to in second drop down and True in the third drop down.
5. Check the Hide this control check box.
6. Click ok until all the windows get closed.