APEX

Hi all pros

I have a button , which is optional if user wants to do so.
"write a note/comment" button
when that button is click ,it should show text area on another region or same region

But the button need to have some value ,
I am setting it to null and , in dynamic action , when button clicked , on condition button value null then display region

BUt not working any idea , what i am doing wrong , what should i do (other work around )?

thanks in advance