It would be a pretty futile exercise as microwave recipes assume you are cooking in a 'cold' oven. The microwaves heat the food by agitating the particles in the food (which incidentally in turn warms the oven) not the oven conventionally heating the food.

If you were to run the microwave empty all you might do is damage the oven and more specifically the magnatron as the oven would have nothing to cook but itself. I'd give the handbook that came with a careful read!

Are you going to use only the convection part of your presumably combination oven. If using convection oven alone you have to heat it as normal. Please remember that a fan oven needs to be 10-15 C lower than the temperature in a recipe.

Mamta