Disable Join Button

Hey there!
I installed bbb on my wordpress site and I’m using the Capabilities plugin in order to let anonymous users join a meeting without entering the code. As the target group is not quite tech savvy, I’m trying to make the process as easy as possible.
Now I have the problem that the Join is enabled from the beginning, and in case the user won’t type in a name in the input form, he will be directed to the mainpage of my bbb installation and not directly to the meeting.
Is it possible to disable the button at the beginning and enable it once the user types in their name?
Thank you for your hellp!