How do you want to use it? Do you mean you want to select records from 3 months/periods ago?
This is a different question to your original post. I suggest you start a new thread with this question. Remember that the quality of the responses will be proportional to the amount of information you provide. Sample documents (qvw/qvf) usually help.
Logic will get you from a to b. Imagination will take you everywhere. - A Einstein