What is the purpose of making these devices into a cell? Is it going to be re-used in other cells? You will have to add pins to the cell to connect through the hierarchy, I'm not sure on how to back annotate the schematic to define the corresponding instances as the components of a block.
If you are only grouping them together to keep them together in this physical design, you can group them in a figGroup. Use the "Group" functions from the Create/Edit menu. All the elements in a figGroup act as if they were one element, moving, copying and deleteing together.