Sculpting and custom axis? i'm using sculpt-mode for terrain meshes. I can lock x and y axis in order to only change the z-pos of the vertices when sculpting.

What I'd like to do is (bit hard to explain): use a 'rotated'(?) coordinate system when sculpting. I need the z-axis tilted a bit for some parts of the terrain map.

I wonder if that is possible ...

Many thanks

Edit:

I hope the following picture helps understanding my question.
You see 4 meshes. I can sculpt the selected one the way I want by locking the x and y axis so sculpting would only affect the z-axis. I'd like to do it in a similar way to the other 3 meshes and move the vertices perpendicularly to the (their!) plane (so in this case the plane would define that axis, but it would be fine as well if the axis could be defined in another way). It would be ok if the different meshes needed to be different objects. But it would not be ok if I had to rotate the meshes for sculpting.
I'm new to this board so I don't know why my previous attempt to answer was deleted. Maybe it was just to short last time so I'm trying to be wordier. Its a perfect solution to your issue because I use this same technique. Its a very simple but it works. and I'm being as clear as possible.
Instead of rotating the view to your object, rotate your object to the view, so that the plane you want to sculpt is aligned with the correct axis. That way you can still lock the x and y, and just sculpt along Z axis.
With the axes locked, you can see that the sculpted verts only move in Z axis.

You can rotate the object instead of rotating the view to keep sculpting only locked to Z axis. Rotated 90 degrees

Even if you dont rotate 90 degrees, you can rotate the object however you want and the sculpting is locked to one axis. The vertices are only moving up. Rotated 45 degrees.