Dual ALV container or screen and subscreens

Hello all, I have an assignment where we basically want to display the output of two standard SAP transactions on the same screen. A simple dashboard if you will. Both transactions are ALV; one is a standard ALV and one is Tree ALV. What I would like to do is display the 1st ALV (standard) on the screen and then when a selection is chosen, populate the tree ALV and put on the bottom half of the screen. I'm not quite sure how to create this. Should I use a screen and subscreen or create a two container ALV using objects? I created a sample dual (two container) ALV but the individual ALV's were not resizable even though I selected vertical and horizontal resizing when I created the containers. Any thoughts would be appreciated. A sample of flow logic would be appreciated also.