That addon's code definitely shows its age... it's still using deprecated awfulness like
getglobal which I wish Blizzard would just get rid of entirely already, and even if it works it'd use a lot more resources than necessary since it doesn't remember the status of items, so it's tooltip-scanning them again every time.
In fact, it was quite disturbing to look at, and I had some spare time at work, so I wrote a new one:
https://github.com/Phanx/BindsWhen
Edit: Tested and fixed a few things. Works fine on default bags/bank and Bagnon. If you need support for some other bag addon, post a link to its download page.
Edit #2: Released, official download page here:
http://www.wowinterface.com/download...BindsWhen.html