Hide/ show layer with the same key..

Hello Everyone,

Can anyone help please...??
I can't create a button that function is to show and close the layer....
for example if I press 'T' to show the transcript, then I want to close the transcript layer with the same key..!!!!
means press 'T' to show and 'T' to hide the layer......
can't do it tried it a thousand times!!!!

I have come up with something with the animations option tried to put the variables but still can't control it properly.!!!!

Thanks,

Nabeel