The paragraph that you want to hide, and the object below it, need to be contained in a subform that is set to Content: Flowed. This will allow everything inside that subform to move up when an object is hidden. If you set the Content of a subform to Positioned, it will place objects at the exact position that you specify when you design the form, regardless of whether other objects are visible or hidden.
Thanks very much. I tried it and it worked correctly. At least now, I know it can be done!