Change text-box style based on condition

please help. i want to change the textbox background color and text color when user check the 'Completed' (checkbox) option. is there any way to do that?

anyone?

Unfortunately, it is not possible to achieve with CSS injection.

It might be possible with custom javascript, but we do not support javascript injections in our form builder. However, if you get a form source code you can modify it and host on your web page.