[Tom Bunch]

Things like start constraints/locked start dates are considered part of the hard-scape of the project. That is, OmniPlan is not allowed to change them in scheduling. It kind of sounds like you are manually scheduling tasks by means like this, rather than giving OmniPlan the ability to help you out.

Where possible, use constraints only when you really mean to hard code that specific date. If your objective is to make the tasks sequential, you can accomplish that via dependencies. If you really need to specifically place each task on a specific date, you'll need to enter those dates manually. OmniPlan could automatically do it, but that would really be at direct odds with the instructions you've given it.

That said, you might get somewhere by just setting the start date of your project, then doing something like this:

tell application "OmniPlan"
	tell front document
		repeat with constrainedTask in every task
			set constraintDate to start after date of constrainedTask
			if constraintDate is not missing value then
				set year of constraintDate to (year of constraintDate) + 1
				set start after date of constrainedTask to constraintDate
			end if
		end repeat
	end tell
end tell

It won't be clever about weekends, so the result may need some fine-tuning.

-Tom