Bank items mouseover?
 

Working on a mod (soon will upload here, I promise!) that adds information to recipe tooltips. Currently I've hooked ContainerFrameItemButton_OnEnter/OnUpdate, which works perfectly well for displaying items in your backpack or in bank bags. That's working fine.

The problem is that if I have an item in the bank, I can't find a function to hook that will reliably fire and alter the tooltip for the bank item. As it stands, you get the tooltip data only if there's at least one bag open (and I surmise this is because of the previous OnUpdate hook).
I cannot figure out how to get this to fire on bank items. Can someone with some expertise point me in the direction of what I'm missing?