How to make object move in exact gametime in Monogame, XNA?

I have recently started learning monogame. The big question i faced is how to make object move, when gametime variable has an exact value.

//Update method in Game.cs
     float delta = (float)gameTime.ElapsedGameTime.Milliseconds / 1000f;
        if (CurrentState != null)
            CurrentState.update(delta);


     if (Keyboard.GetState().IsKeyDown(Keys.Enter))
            SetState(new GameState());

    //GameState.cs, there is a box that's need to be moved in 5 seconds
    Vector2 boxpos = new Vector2(800, Game1.graphics.PreferredBackBufferHeight / 2 - 100);
    float olddelta = 0;
    public void update(float delta)
    {
        float newdelta = delta;
        if (newdelta - olddelta >= 5)
        {
            boxpos += new Vector2(0, -200);
            olddelta = newdelta;
        }
    }

I’ve drawn a box in my gamestate’s draw method using spritebatch.Draw(Box, boxpos, null, Color.White, 0f, Vector2.Zero, 1f, SpriteEffects.None, 1f);, but it’s position remains constant.
I really have no idea how to do it in a right way. Hope can receive some help.