SQL-Server will do this for you.
Assuming you have auto create statistics and auto update statistics on
(which is the default), the statistics will be updated regularly.
Whenever statistics for a table/index are updated, the query plans that
use these tables are invalidated. The next time the query or stored
procedure is run a new query plan is determined.
You can also force a stored procedure to be invalidated, either by
applying sp_recompile to a table or by applying sp_recompile to a stored