creating a materials function that change at the space ot a solid 3d elementes

hello,
i have a problem with my model
i want to change the materials properties ( young modulus ) every iteration
without change the model geometry.
for example a 3d slab (one block elements)
and i want a young modulus equal to 30e9 from x=0 to x=6 and y=0 to y=2
and at the rest i want young modulus equal to 45e9
can i do such a thing with comsol?

thanks,
rony