There isn't a way to do this in version 4...

But in version 5.0 (www.axure.com/axurerp5beta.aspx), it is possible to create this type of animation (even though it is a little bit of a "hack"). We are planning to fully support this in the future, but for now, I have attached a sample file of the workaround.

Start by adding a case to the event that triggers the animation. We need the event to behave as if there was a condition on the case so we add a condition to the case that we know will always be true (i.e. OnLoadVariable = "" assuming we aren't using that variable for something else). Then add the set panel state action for the first action in the animation.

Next add a second case. This time you don't need a condition, you can just create the second set of actions in the animation. These actions will include the Wait action (which should be the total time from the start of the event to when this action should be executed) as well as the set dynamic panel action. In the interaction tree, we need to change the "Else If" to and "If" so that the second case will also always occur. To do that, right click on the second case and use Change to IF.

Repeat for 3rd, 4th, etc. cases.

Not elegant yet, but it should work.