Alinco SORTA does this, in that it's supposed to tell you what scrolls you're missing either from just the schools you have trained or all schools.
One other feature of Alinco is it will allow you to use a global spellbook which tells you what scrolls are missing from ALL your characters, when you're on one character, as an example, a creature drops a scroll and your logged off mule needs that scroll, you will be alerted that you need it.
This can be confusing if you're using tradebots as it will tell you that you need ALL these scrolls, when in reality, it's just your baby mule that needs them. For your non-active characters, you have to disable 'Use global spellbook' so this doesn't happen.
You can find Alinco here:
http://acheaven.buwahaha.com/