I will post my reply here too, just in case others find this later. If it trys to calculate as you move your mouse around constantly, I am afraid that will create an overall slow down in your game, as it keeps trying to calculate many many paths. Every vector3 move would start the calculation on the next path, as the previous one was still in progress. Its a lot of paths. I am not sure how many concurrent paths nav mesh can handle.
One possible solution is for the game to not calculate the path until your mouse stays still until X amount of time. That could limit the amount of path requests. That is something you could do with the logical of playmaker.
There is no one solution that will solve this movement issue unfortunately. It will take even in playmaker, a fairly complex bunch of FSM to re-create this game mechanic (overall, with movement, action points, etc).
This is my tutorial on point and click movement using navmesh. If you wanted to use navmesh for pathfinding, this would likely be how to setup the first part.
The second part would be to use agent destination distance actions to calculate the distance and then float compare to see if it is within the distance.
Third, you would need a line renderer type action (you need a custom action, nothing in playmaker for this), that would draw the line if within the distance, or change color or something.
Lastly, you would need to then block movement if the distance is too far.