Ok, the only other thing I have found is this:
it is for DeskI and i have gotten it to work, (in DeskI) but have not tried to convert the logic to WebI. If you have access to DeskI you might want to try it and then see if you can use similar logic to get it to work in WebI.
I have not found any other information regarding Trend Lines, hopefully someone has additonal ideas they can share.
REB01 
(BOB member since 2004-11-29)