Slicing Objects

Hi,

Please see attached.

I have an assembly that contains multiple parts. I would like to cut away all areas except a rectangle section that includes some of the holes for faster FEA simulations of only the areas of concern.  Is there a way to cut away the unwanted areas on multiple parts at once? I have about 10 layers total but have included 2 here to simplify it and hopefully just to get an explanation on how to do it. I am new to Creo so as detailed explanation as possible would be greatly appreciated but anything is better than nothing. Thanks in advance