C# - Gradually filling a rectangle using a timer and a trackbar to control the speed

I am having issues trying to figure out how to fill a rectangle by using the trackbar value to control the speed of the fill. Imagine water flowing into a cup, so the water pours into the cup but the speed of the water flow is controled by the trackbar's value. I can't get it to fill from the bottom up. It starts from the top down, which I need it to fill from the bottom up instead. My code is below:

    private void trackBar_Scroll(object sender, EventArgs e)
    {
        trackBarSpeed = trackBar.Value;

    }

    private void tmrTimer_Tick(object sender, EventArgs e)
    {
        timerCounter++;

        Graphics graphics = CreateGraphics();
        Rectangle rectangle = new Rectangle(81, 201, 219, (10 + timerCounter) * trackBarSpeed);

        graphics.FillRectangle(new SolidBrush(colour), rectangle);
    }