Forms Data Controls :: Adding New Items To Repeater Control With Transitions?

I am currently in the process of writing a facebook type 'activity feed' for a site. Currently I am binding the last 10 items to a repeater control, which contains a usercontrol representing each item. The requirement is that when a user clicks a refresh button any new events are added to the top of the list, the previous items drop down and the equivalent number of old items drop off the bottom, all with nice slider transitions. I have put the repeater inside of an update control and are able to handle the transitions by using RegisterStartup script to drop jquery calls onto the page for the slider. However I cannot find a way to dynamically add or remove new datarows to the repeater.

I need the old items to stay in the repeater and be pushed down by the new items, so completely refreshing the datasource seems like a bad idea.I was thinking about maybe storing the datasource in the viewstate and adding rows to that, maybe with an extra column on the end which stores what transition is needed on the databind for my jquery, but there will be a 'View more items' link at the bottom of the page, so I am worried that the list could get pretty large and there would be a big problem with memory.