If i understand correct you have a list and under that list you a have an object that is linked to it.
For better understanding i will go with the assumption your linked aggregate is in fact another webblock.
In thaat case you have an inputparameter in that webblock and you can refresh your linked aggregate in the OnParameterChanged event.
However, this could generate a lot of server calls.
If you know which items should be refreshed (for example only those that are visible (in case of selecting items to display detail. then you can narrow it down by checking if the items should be refreshed or not.
I hope you are a bit closer to your solution.