SQL Server Agent – How to Stop Job After Certain Hours

Turns out I was connecting to a Load Balancer which redirects me to either one of 2 sql servers which are synchronized ( for better performance) the SQLServer Agent was turned on on one of the servers but it was off on the other server. I needed to create my job on the main server (which has the agent service running). I didn't know we had 2 SQL servers that were identical and that I was connecting to a different one every other time. Sorry about that, but thanks again for the helpful comments, I found some interesting things in the error logs that helped me figure this all out. Thanks again!

Using Kenneth's code, and a few other bits and pieces that I pulled together, I came up with the following code which I think should do the job. If anybody sees any potential problem with this I'd be interested in knowing!

-- Check if this server is the preferred replica for backups.
    If sys.fn_hadr_backup_is_preferred_replica( @DatabaseName ) <> 1
    BEGIN

        -- Check whether the script is running from SQL Agent.  If it is not then raise an error so that the user knows that the backup hasn't completed.
        -- (If the job is run from the agent then there should be an equivalent job running on the preferred replica, so no need to alert).
        declare @AgentAccount varchar(100)
        set @AgentAccount = (select cast(value_data as varchar(100)) as [AccountName]
                                FROM sys.dm_server_registry
                                WHERE registry_key LIKE '%SQLSERVERAGENT%' --For named instance change to SQLAgent$<instanceName>
                                AND value_name = 'ObjectName'
                            )


        if @AgentAccount = SYSTEM_USER
        begin

            declare @jobSource tinyint
            SELECT  @jobSource = ja.run_requested_source
                    --WHEN 1 THEN 'SOURCE_SCHEDULER'
                    --WHEN 2 THEN 'SOURCE_ALERTER'
                    --WHEN 3 THEN 'SOURCE_BOOT'
                    --WHEN 4 THEN 'SOURCE_USER'  -- This one is manual
                    --WHEN 6 THEN 'SOURCE_ON_IDLE_SCHEDULE'
                    --ELSE 'UNKNOWN' END
            FROM msdb.dbo.sysjobactivity ja
            WHERE ja.session_id = @@SPID
            AND start_execution_date is not null
            AND stop_execution_date is null;

            if @jobSource = 4   -- Job was run manually.
            begin
                RAISERROR ('No backup produced as this server is not the preferred replica for backups.  Please run the script again from the preferred replica.', 16, 1)
                return 1
            end
            else
            begin
                print 'No backup produced as this server is not the preferred replica for backups.'
                return 0
            end
        end
        else
        begin
            RAISERROR ('No backup produced as this server is not the preferred replica for backups.  Please run the script again from the preferred replica.', 16, 1)
            return 1
        end
    END