How to add empty rows into dynamic subform

I created a dynamic subform which flows and repeat subform for each data item. I also put a summary next to it.One page can only contains 30 rows of the subform,and if row number is bigger than 19 the summary will flow to the second page.
My question is , I want to put empty rows into this subform. For example if 20 rows come in, I need to put 10 empty rows into the first page and put 19 empty rows into the second page.
Is there any functions in livecycle desginer could realize it without script?
If there is no way,how to make it through script?