Crystal reports 2008: keeping two detail section together while printing

I have two detail sections as below with no page header section.

      detail a

      detail b

I am using the detail a as a header for detail b. detail b has large content going up to anywhere from 3 lines to two pages. I wish to keep detail a and detail b together while printing. I have checked keep together for the outer details in section expert which kind of works when detail b has few lines but when detail b goes to 2-3 pages, I have detail a in a new page ( blank page ) and then detail b follows in a new page. How can I avoid the blank and combine the two together.