If you've ever played with "Related Dates",   note that you can do some cool stuff with the extension.
 
 
This rule in a Text Folder
Code:

++:MI+-!:[Related Dates]:[Related Dates] 

 
 
will get your started....
 
 
11 00050807030742080090cc0d 0 0 0 +00001
 
(the red part is the day offset,  and the green digit is 1 if the item is the 'base')
 
 
everything to the left of green is ID# for the related 'group'
 
 
 
(you can create your own groups,  modify relations, etc. etc.)
 
(you can test for relations, times, etc. etc.)
 
 
the second and third 0  are for 'count only business days'  and 'schedule only on business day' flags.
 
 
 
A most basic application for this would be,  for example,  NOT TO MODIFY a date if it is a related date.