How do I start with this? Any ideas?
Here’s something I modified from this site. It cycles through each item in a selection of multiple. This can get you started.
tell application "OmniFocus"
tell front document
tell content of document window 1
set SelectedTasks to value of every selected tree
if ((count of SelectedTasks) < 1) then
display alert "You must first select an item to complete." as warning
return
end if
repeat with anItem in SelectedTasks
set estimated minutes of anItem to 5
end repeat
end tell
end tell
end tell