property pDaysBefore : 14

tell application id "OFOC"
	
	tell front document window of default document
		tell content
			set lstTask to value of selected trees where class of its value is task or class of its value is inbox task
			repeat with oTask in lstTask
				tell oTask
					set dteDue to due date
					if dteDue is not missing value then
						set start date to (dteDue - (days * pDaysBefore))
					end if
				end tell
			end repeat
		end tell
	end tell
end tell