This won't add the actual functionality of a timed status but it gives them something to make it appear like the server is working by adding an animated gif during the time of upload. It only appears during the upload and dissapears once it's complete.
In the attachmentbit template find:
Code:
<div align="center" id="uploading" style="display:none; margin-top:$stylevar[cellpadding]px">
Add this below it (change the path to your own and add this image):
Code:
<img src="http://www.yoursite.com/images/uploading.gif" width="153" height="11">