Diane,
Open a blank query in design view, and enter 21999 in the Field row of
the first column of the query design grid. Make it an Append Query
(select Append from the Query menu), and nominate your table. In the
Append To row of the grid, enter the name of the Autonumber field. The
SQL of the query will look something like this....
INSERT INTO [YourTable] ( YourAutoNumberField )
SELECT 555 AS Expr1;
Run the query (click the toolbar button with the red [!] icon). Close
the query, open the table, and selete this record just added. After
that, the next record added will have 22000 in the autonumber field.