nope. what i mean is doing undo operations on a project as opposed to a buffer. lets say you have 3 buffers open and you edit buffer 1 (i), then you edit buffer 3 (ii), then you edit buffer 2 (iii), and then back to buffer 3 and you edit it some more (iv). finally you want to do project-undo from this point in buffer 3. the undo sequence then goes like this:
(iv) - (iii) - (ii) - (i)