Button to turn closed caption on and off

I’ve been working on a narrated course in Captivate 5.0 that must be 508 compliant.  I’ve set the click boxes to continue to the next slide using the Tab key.   ( Thanks to  Liybiri) I’ve inserted the seamless tab script in the htm so it doesn’t wander to the explorer.. But the tab still jumps to the playbar. How can I get a button for the Deaf to use to turn closed captioning on and off without using the playbar.