Batch convert bitmaps to cmyk and fixed max resolution

Hi

I do brochures and other marketing material for schools including prospectus. Due to having dozens of high res photos the file size becomes very large. A 24 page document is taking 600mb. This slows down saves as well as reduce overall performance. I would like to resample as well as convert from rgb to cmyk for all photos even those in groups and powerclips. I tried to look around but either they don't do anything on corel x8 which i am using, or they go through the motions and do nothing.