Complex data sort needed across 3 columns

I have a spreadsheet where I want to return a subset of rows.

There are 3 relevant columns: A, B, and I. They are all text values.

1. I want to return all columns where column A="B" ("B" is a person)
2. Of that subset, I want to see all rows where column I does NOT equal "P" ("P" is a location)
3. Of that subset, I want to see all rows where column B's text value "blah" (a task) doesn't also exist as the column B value in the subset of rows where A="B" and I DOES equal "P".

In other words, me, a person, am going to location P today, and I want to find out if there is a task that I can do there that hasn't been done there before, but HAS been done at a different location.

Thanks!