Comparing two tables?

I have two tables which has similar structure.
table1:
INDEX DETAILS
001 ABC
002 DEF
...

table2:
INDEX DETAILS
001 ABC
003 XYZ
...

I want to compare the INDEX of these two tables and only store records (in table3) that are not duplicated. So in this case table3 should look something like this:

table3:
INDEX DETAILS
002 DEF
003 XYZ
...
i.e. record 001 is drop because of duplicate INDEX

How do I achieve this? I have tried using 2 "Do Until rs.EOF"s but it does not work :(

Thanks!!