Assuming they were loaded uniformally, build a table of suffixes with a
totals-make table query.
SELECT Trim(Right(YourTable.[LastName],3)) AS Suffix INTO SuffixList
FROM YourTable
GROUP BY Trim(Right(YourTable.[LastName],3));
Then run an update on new Suffix field in your table using
SuffixList.[Suffix] as criteria on calculated field -
Trim(Right(YourTable.[LastName],3))
If they were not uniform -- Jr, JR., Sr, Sr., 2nd, II, III, 3rd, etc - then
add another field to the SuffixList to put standard suffix and then use it
for update.
Lastly update the LastName field with --
Trim(Left([LastName],
Len([LastName])-Len(Trim(Right(YourTable.[LastName],3)))))