You would probably have to use Custom obstacles for the Pathfinding behavior, and have invisible obstacles all over the screen, so that when you place a path, those obstacles get destroyed and you can regenerate the obstacle map around the object. Because what you want is basically to specify where the object can move but the Pathfinding behavior only allows you to specify where it can't go.
Here's an example: https://www.dropbox.com/s/85nsk1k5u3z8wrb/Path.capx?dl=1
Use the left mouse button to place paths and click the right mouse button to move the character.