Changing navigation title programmatically

I have a navigation bar with a title.
When I double click the text to rename it, it actually says it’s a navigation item, so it might be that.

I’m trying to change the text using code, like:

declare navigation bar as navagationbar here
button stuff {
    navigationbar.text = "title"
}

That’s not my code obviously, just showing how it would work.

So whenever I press the button, I want the title to change.