Passing information between form segments

I have been trying this and am not sure if this doable or not.

I have 2 form segments on 1 main form.

Segment 1 has a grid in which I would like to select a row of in order to display the detail in segment 2.

Segment 2 is driven off of a business object and requires one parameter (the one from the grid).

In which ways can I accomplish this?  Is there a recommended approach when working with segments? Thx for the help.