The "Highest Rating (in last 30 days)" helps, but if that rating exceeds the banded range, after the player has entered, he is still paired anyway.
Example: April 06 Grouped Banded 1600-1699 Tournament 1065
which started 18-Apr. Wuffell User 195025
has been rated outside the banded range since 11-Apr, yet was still paired.
Can other examples, maybe in other tournaments, be found? How about in the Easter '06 Grouped Banded 1200-1400 Tournament 1079
which started 13-Apr where player badmoon User 229517
had been over the banded range since 9-Apr. There are possibly examples from the lower side, but the 30 day cushion makes these are a bit more difficult to spot.
So a solution might be a script which selects banded tournaments and makes sure the "Highest Rating (in last 30 days)" is still within the banded range. Possibly a pm to let the player know they no longer are within the rating band for the tournament with the entry removal? If it were ran regularly a player could possibly enter into the next tier of the banded tournament.