I am no expert in Pocket PC's unfortunately, but basically as far as I understand it all depends on the software that synchronizes Pocket PC with the desktop PC. If it can synchronize data with a program that supports export to CSV (for example, ActiveSync supports synchronization with Excel as far as I know) then you can export data as CSV from Excel and then import the CSV files into Aware IM.
Also if a browser on a Pocket PC supports HTML 3.2 and JavaScript then you can access Aware IM server directly from the Pocket PC