How to Determine when a component is loaded

I am using CS3 and have 4 layers and 4 frames on the stage. I load all xml and code in frame 1. Frames 2, 3, and 4 have list and combobox components.

I want to populate the list and combobox components with the xml data from the code in Layer 1, frame 1. But this is not happening because of the load sequence.

I would like to know how to listen for the list and combobox loading and then populate them. A light on how the load sequence works would be very helpful in addition.