Hi Baron,
You should be able to do this using Change Order Transitions, which will restrict the ability to update a change order's status from one status to another, and can have a condition attached to it such that it restricts the update if the condition is not met. In your case you would most likely update the transitions that you want to restrict to add a condition to them. You can create the condition first and then add it to the Change Order Status Transitions that you need to enforce this on.
Here is a screenshot of the creation of the condition macro:
And here is a screenshot of the condition you would create:
Now I have not tested this completely but I think it will help get you in the right direction on this. That would be the best way to restrict the status on from being updated if the wf tasks are not all complete.
Hope this helps,
Thanks,
Jon I.