Well I've read the related questions-answers but still cant find a way to move my champion to the mouse position after a right-button mouse-click. I use this code at the top:

float speed = (float)1/3;

And this is in my void Update:

  //check if right mouse button is clicked
        if (mouse.RightButton == ButtonState.Released && previousButtonState == ButtonState.Pressed)
        {
            // gets the position of the mouse in mousePosition
            mousePosition = new Vector2(mouse.X, mouse.Y);

            //gets the current position of champion (the drawRectangle)
            currentChampionPosition = new Vector2(drawRectangle.X, drawRectangle.Y);

            // move champion to mouse position:
            //handles the case when the mouse position is really close to current position
            if (Math.Abs(currentChampionPosition.X - mousePosition.X) <= speed &&
                Math.Abs(currentChampionPosition.Y - mousePosition.Y) <= speed)
            {
                drawRectangle.X = (int)mousePosition.X;
                drawRectangle.Y = (int)mousePosition.Y;
            }
            else if (currentChampionPosition != mousePosition)
            {
                drawRectangle.X += (int)((mousePosition.X - currentChampionPosition.X) * speed);
                drawRectangle.Y += (int)((mousePosition.Y - currentChampionPosition.Y) * speed);
            }
        }
        previousButtonState = mouse.RightButton;

What that code does at the moment is on a click it brings the sprite 1/3 of the distance to the mouse but only once. How do I make it move consistently all the time? It seems I am not updating the sprite at all.

EDIT I added the Vector2 as Nick said and with speed changed to 50 it should be OK. I tried it with if ButtonState.Pressed and it works while pressing the button. Thanks. However I wanted it to start moving when single mouse clicked. It should be moving until reaches the mousePosition.

The Edit of Nick's post says to create another Vector2, But I already have the one called mousePosition. Not sure how to use another one.

            //gets a Vector2 direction to move *by Nick Wilson
            Vector2 direction = mousePosition - currentChampionPosition;

            //make the direction vector a unit vector
            direction.Normalize();

            //multiply with speed (number of pixels)
            direction *= speed;

            // move champion to mouse position
            if (currentChampionPosition != mousePosition)
            {
                drawRectangle.X += (int)(direction.X);
                drawRectangle.Y += (int)(direction.Y);
            }
        }
        previousButtonState = mouse.RightButton;