They make special hangers just for this purpose. It is a octagon shaped box with an expandable arm that reaches across the drop ceiling grid sections. They adjust sideways and up and down. Any HD, Lowes or supply house will have them. Just describe what you want to do and they should be able to fix you right up.
Thanks - I saw those boxes yesterday but wasn't sure if they would work. Well, now I do. I am on my way to Lowe's. I also like the other solution however I would think they are a few $$$. Have a great day.