To addon to Lowell post you could also check for the existance of the flag and then start the job; otherwise, just finish up

IF EXISTS(SELECT STATUS FROM SOMETABLE WHERE STATUS='READY')

BEGIN

EXEC msdb.dbo.sp_start_job N'MyJob';

END

ELSE

BEGIN

INSERT INTO TBLOG(MSG,MSGDATE) VALUES ('Status was not ready at this time',getdate())

END

You would have to reset the value at the end of the second job, "MyJob".