Tables do not have a 100th row. . . If you want some unpredictable set of rows you could declare a curaor for the table, open the cursor, fetch and ignore 100 rows, continue to fetch rows and process them until you reach 1000 and then close the cursor.
This will get the number of rows you said you want, but is not worth much as a solution. If the query is run again later, the rows used are likely to be a different set of rows.
Hope this helps,