Ken1171 has a script in the marketplace. P11 or P12. Does exactly what you want plus it does it by instancing so the memory footprint of your group is much tinier than duplicating the items or groups repeatedly. The Scatter Tool. I have the P11 one. Very useful for just this type of thing. Single table instanced in any size grouping with a single chair. There can be multiple table groupings on a patio of a table and single or group of chairs all of which are instances and attached to a grouping object. I use the P11 version and will purchase the P12 version soon come. Worth while for a number of reasons.