HI
Since the content is dynamic we can't split or keep together with previous page or next page.
Try with Keep Together function through Section Expert, also if your text is placed in Group then go in Change Group--Options-- Keep Group Toget option.
Also right click on sub report and go in Format sub report--Common tab-- Keep Object together option.
Also you can play around by inserting new page before or after conditionally. ie. counting lines and if the count is > or < then you can insert a new page.