This article has the syntax for sp_purge_jobhistory. You may create a job which executes a query similar to the one below. This query deletes records older than 10 days.
DECLARE @oldestdate DATETIME
SET @oldest = GETDATE() - 10
EXEC SP_PURGE_JOBHISTORY @oldest_date = @oldestdate
Pradeep Adiga
Blog: sqldbadiaries.com
Twitter: @pradeepadiga