Design Via Stitching for a specific area(-15GND)

[saeednowroozi]

Hi all,
I want to use Via Stitching for a specific polygon(-15GND). But I can draw it only for GND and draw on all surface boards. What method do you suggest? sample photo.

[qdrives]

Which EDA tool?
In Altium: Tools / Via stitching/shielding / Add stitching to Net

[saeednowroozi]

I work with Altium 2014.
When I specify constraint Area , after that it gives this error.

[qdrives]

Is it possible to place via's? This is not possible if there are other tracks, polygons or planes below the area.
You could also place them manually if the area is not to big.