Add To-Dos and who they are assigned to as a filter on the lead table

We often want to send communications out to those on the to-do lists of certain employess. So, if we have a to-do to call 20 people and none of them have a working phone number, we want to send all those people a letter. Even a way to tag a bunch of records based on the fact that they all have the same to-do for the same staff member would accomplish our goal.