How to maintain the space between two elements if the other is Repeating group?

Hi,

How to maintain the space between two elements when the upper one is Repeating group?

Element B is a Repeating group (ext. vertical scrolling). There might be 2 items or 200 items in it. How to maintain the space D fixed? It doesn’t have to be exact the same in all cases but more or less. If it matters the A and B elements have static info so their height will be static.