Move a character a set distance on NavMesh

Hello all,

I am trying to move a character a set distance per turn. For this I currently use the following script:

 pathDifference = pathCurrentPosition - pathStartPosition; //CurrentPosition = Mouse Position
 pathDirection = pathDifference.normalized;
 pathDistance = Mathf.Min(selectedUnitMovementRange, pathDifference.magnitude);
 pathEndPosition = pathStartPosition + pathDirection * pathDistance;

This also works very well so far. The problem is that only the start and mouse position is included in the calculation. If the character should walk around a wall, he can walk much further than he should.

I have already tried to adding the difference of the individual points via a loop. Unfortunately without success.

Does anyone maybe have an idea how I could solve this problem?