I just checked your chart (www.astro.com - go to Free Horoscopes and then Extended Charts and you'll be able to see it) and it's true that you don't have a Grand Trine in your chart (it would look like a blue equilateral triangle).
Grand Trine's occur between like Elements:
All 3 Air signs
All 3 Fire signs
All 3 Earth signs
All 3 Water signs
You actually do not have any aspects between your Mercury and your Venus - but you do have an opposition between your Venus and Saturn.
You might want to check out www.astro.com for more information - and I have some learning sites on my own site...