manipulating position.y in unity

Hello, i'm trying to create script that will push player to the sky and if it reach equal lvl, it will fall down.

Here's part of code

 if (controller.isGrounded) {//if controller is on the ground
             isFlying=false;//set that it is not flying
 
             if (Input.GetButton ("Jump"))//if button jump
             {    
                 isFlying=true;//the thing started to be in air
                 jumpReached = false;//but it doesnt reach the max altitude
                 jumpStarted=false;//the jump mechanism is not started yet
 }
 
         }
         if (isFlying == true && jumpReached==false && jumpStarted ==false) {//if thing is flying, the altitude is not reached and jump procedure is not started
             moveDirection.y += 0.9F;//set object 0,9 above ground block
             maxJump = moveDirection.y + 10F;//set altitude 10 blocks above ground
             jumpStarted = true;//initial jump procedure ended
         }
         else if(isFlying==true && jumpReached==false && jumpStarted ==true)//if thing is flying, altitude is not reached and jump has started
         {
         if (moveDirection.y >= maxJump)//if altitude reached
                 {
                 jumpReached = true;//now its time to fall down
                 maxJump = maxJump - 10F;//refreshing maxjump 
                 }
             moveDirection.y += 3F;//if not give the player strength to fly to the air ;)
         }
 if (isFlying==true && jumpReached==true) {//if player is in the air and it should fall down
             {
             moveDirection.y -= 0.95F;//decrease player position by 0.95
             controller.Move (moveDirection * Time.deltaTime);
             }
             if(controller.isGrounded == true)//if player is on the ground
                 {
                 isFlying =false;
                 jumpReached = false;
                 jumpStarted=false;
                 maxJump = 0;
                 }//reset everything
         }
         moveDirection.y -= 0.60F;//if nothing happens players is going to fall
         controller.Move (moveDirection * Time.deltaTime);

The problem is that I can't compare position of player to maxJump. Any idea?