DSXchange

Is it possible to use a value returned by a DSMacro and update a Env Variable dynamically, without using shellscript??

what i want to do exactly is, get the DSJobStartTimestamp and use next time job runs and extract data greater than that timestamp.

Dynamically No. You would need to land it somewhere else, maybe a file or a database and read it the next time, you run the job.

A DataStage macro can only be run from within a job.

However you can do this with a routine, using DataStage API calls (specifically DSAttachJob(), DSGetJobInfo() and DSDetachJob() functions), but you'd need to do this before starting the job itself.