I would just write a vb script for this within project, but the locked flag is only accessible from PWA.  So we wrote a quick C# application but the DraftTask.IsLockedByManager flag doesn't seem to work.  It almost appears to be a bug.  Can someone point me in the right direction.  We need to lock a task from further input after X happens.  Locked does the trick, but it doesn't seem that you can set it Programmatically. 

You can't lock anything in Project Pro. Are you sure you're not locking SharePoint tasks in PWA? They are not the same as Project pro tasks.