"after-create" event for panel?

"after-create" event for panel?

Hello,

i want to add a class to a specific element in a panel, after its completly created/loaded.
But using event "create" does not work. "beforeopen" does work, but i dont want to fire it every time the panel opens.
Is there a solution like "after-create", that fire one time when panel completly has beend created?

Thank you