Hi Sasi,
There are many ways to schedule such requests, the easiest way i feel is call the job chain B as last step of Job chain A, in this case job B will start after completion of all steps in job A and as the chain B is child of job A, ideally two jobs will not run in parallel, to avoid any chances of parallel run add locks as suggested above.
and the other method is create one event XYZ and add this as raise event in Job A, and as wait event in Job B, here once Job A finishes it will raise event XYZ which is wait event for Job B so the job B will trigger once job A finishes. add locks in Job A and Job B.
KR
Muhammad Asif.