The active ingrediant in Preen is Trifluralin a mildly toxic chemical. Properly applied to your soil it will prevent new weed growth, it interferes with seed germination, just as Corn Gluten Meal does. Since the carrier for the Trifluralin is ground corn cobs many people may think that the product is CGM when it is not.
Corn Gluten Meal is a much more environmentally friendly weed growth suppressor which may not be needed by those of us that properly mulch our planting beds.

Preen has an "organic" form also. Contains corn stuff.

I will look for the non-toxic corn gluten. I mulch my ornamentals but have never mulched the veggie beds. Any opinions on the surface burning to get rid of the seeds from this years weeds? Or will corn gluten applied now cause these seeds to not be able to germinate next year? I usually put shredded leaves and bunny manure juice on my beds in fall, will that be okay to put over the organic Preen or corn gluten?

Corn Gluten Meal should be applied to prevent seed germination about 6 weeks before that is to happen and it has a fairly limited life for that prevention, so applying CGM now to prevent seed germination next spring would be a waste of your money, time, and energy.
Burning might be illegal in your area of the world, or may require a permit with strict limitations. Some people with prairies for yards do burn, because their plants need that for some of the seeds to germinate. Burning would not be a solution for "weed" control.

I found the CG at our Agway and will need to re-apply often, no problem it's a small area. The burning I mentioned would be too ruin the weed seeds now on the soil surface from nearby weeds. I would apply straw and let it burn just long enough to ruin those weed seeds on the soil surface. It's a small area, and thenuse the CG once plants are planted next year. Maybe burnng is nutty, but it was raining weed seeds and I kinda want em gone.

Preen is a joke once you have a little hole in the soil surface weeds comes out very vigorous. I am looking for a weed retardant to spray few weeks before planting. What the commercial growers do I saw a big field of water Crest without one weed in it how this happened. There is a weed retardant which kills the seeds and allows you to put your plants or seed few weeks later. That is what I am looking for. Really weeds drive me insane.

Homeowners tend to spend far more money on stuff they do not need then do commersial growers who are watching their bottom line. The more money a commercial grower spends on things like weed controls and fertilizers the less their profit will be.
Most all pre emergents will allow seeding several weeks after that pre emergent has been laid down, just follow the directions that should come with the product.

I will try the CG, I have a 50lb bag now. It was $25.00 for it. I have a role of erosion control fabric, also. It's like very good weed block fabric, water passes through, but weeds don't. It's light green so the sun shouldn't make it hot. I will try it next year. I will have to apply the CG around the stems where the holes for plants are, after planting next spring.

Not sure if it's the same where you are, but in Douth Florida I've found that weed block fabric is a waste of money and causes more work in the long run. Weed seeds don't come from the ground, they come from above ground. So as soon as you lay mulch you have a breeding ground for weeds to grow. I'm looking for something that will stop the trillions of bishofia seeds that fall in February and March from germinating. I spend the whole summer pulling them! Any ideas?