How do you do it?
Position your cursor on the desired region, and press ctrl+R. Or click on the cursor button on the render pallete and drag to the desired region of canvas.
Thanks jramauri 
Do you know if the area can be bigger region from cursor?
OK I think I see how it works do from cursor when done move some then re-do do from cursor and repeat as desired.
Exactly. As far as I know, there’s no field or button to define size of a render region, you just made render region repeatidely.