Can anybody point me to the file that runs the automatic "X Cancel" button on a flypage? I simply want to change it to "Back". Cancel seems a little weird.

view.html.php :

function displayXxxx() :
Second parameter is a language string.
You can create a new language string,
or change this string for all your component, in the language file.

In this case, this is a global native string, so the best is to create a new one.

By the way, the native Toolbar helper is available here :
There you can understand better wich parameter correspond to wich button.