Date custom attribute automatically set when state changes.

Hi Guys, please help me on this:

I'm working on an update in my project and i want to know if i can and how to do this: I have 4 date attributes in my WorkItem Type. 2 of them work as expected but I'm not the one who has done it and i need to reproduce it to the other 2.

Creation Date set automatically the current date with hour/minutes/seconds when you save for the first time, state from unassigned to new. With Resolution Date the same, when state change from anything to Resolve, it automatically get the current date.

I've 2 others custom attributes: Returned Date and Replied Date. Returned when state become "return to submitter" and Replied when state become "Reply" that i want to be automatically set.