At the end of this thread you can find the code to detect if a job is running or not and all you will have to code after that is someting like

exec sp_startJob ...

DECLARE

 @job_name sysname,

 @status tinyint

WHILE 1=1

begin

EXEC DBA..af_Job_Status 'YourJobName', @Status OUTPUT

IF @Status <> 0 --Not Done

  Wait for '00:00:01' --1s

ELSE

  Break

end

another option is to fire the next job at the end of the previous one and create like a job chain. It is not pretty but you don't have to code... your choice

hth