Hi, just picked up your post. If its not sorted i have a thought on how it could be done . But my solution would us days not weeks , As apart from February ,months have more than 28 days. When you say a child is 6 Weeks premature is this a round up or is it exact number of weeks ? .Hope this is clear for example 6 weeks is 42 days which could be one month and 12 days or even one month and 11 days .Using 4 weeks per month would not be so accurate . Let me know it you wish to see my attempt and let me know what version of access you have .
Regards