[Tkinter] bind

[menator01]

I have a listbox. I can bind keys, mouse clicks, etc. to fire a function. I have selection_set and activate set to 0, the first item in list.
My question is there a way to have the function to fire when the list is produced , so I can show/get the data from the first item that is set as default?

I hope I am clear on my goal. If not I will try to explain better. I can post all the code if that will help.