order topitems by a dynamic data field

hi everybody,

I have a publication type that works like a TODO list, and I'm using
the topitems block to show te latest five on my index page. This pub
type uses a DD field to store the deadline for the task, so I need to
show the top5 items sorted not by the creation date but by this date.

How could I do it?

Thanks 

-- 

Rodrigo Lazo (rlazo)