It depends how you'd like to run the task based on your SQL job.
I usually run my task only if the load in DB is complete, for that I've created a view in db.
By creating a loop script in your qvf and having other tasks dependent on the loop file. If the load is successful, your task would start, save the qvd with new time stamp.
There is more to it.... not sure if you looking for this?
I already configure a job who runs continuously/each 5 minutos and detect a field like "updated=yes" then run the load script. Just check on SQL Server workflow a possibility to add a new step like run a batch job.
Complementing what Felip said, you can use this very useful powershell wrap by Adam Haydon to prepare your script:
Hope it helps,
When you say SQL job, do you mean and Scheduled SQL agent job? If so can you not look at the task history of week the schedule runs and how long it takes and create a task schedule for the Reload task that mirrors that with a buff of nnn minute greater that the SQL job max run time?