How to keep track of equipment in equipment group

Hello,
Can anybody please tell me that how can we keep track/history of an equipment in equipment group?

For eg, I have an Equipment group A, which consists of 3 equipments (Equipment 1, Equipment 2 and Equipment 3). Now if a user deletes equipment 3 later on and adds another equipment (Equipment 4) into it. Then how can I keep track of it?

Regards,
Janesh