Raj,
Using the query designer...
1. Make a new query. Do not add any tables to the top panel of the
query design window.
2. Type 999 into the Field row of the first column of the grid.
3. Make it an Append Query (select Append from the Query menu), and
nominate your table as the table to append to.
4. In the Append To row in the first column of the grid, enter your
Autonumber field.
5. Run the query (click the toolbar button with the red ! icon).
6. Close and don't save the query.
7. Open the table datasheet and delete the newlay appended record.