Modifying the file browsing system

[mschneider]

I've written a very simple plugin that basically has a yes/no setting option and then saves a file indicating the setting (0 for no, 1 for yes). I've written a function to read the file and then set a variable to yes/no based on the value written to the file.
What i am trying to do is modify the file browsing system so that everytime you enter a directory if yes is set that something happens (e.g. a splash "Yes"). I've tried modifying apps/filetree.c in the functions ft_open and ft_load but every time i do this whenever i enter a directory i am either presented with a data abort or a blank screen. Any suggestions as to what file i should modify?