Bruno, i think the whole "box of members" is not working. For example the table doesnt list when a member has crossed the line for the membership. (i.e. it should turn red when the end date passed "today". ) So when a member pays for the next year, it lists him as having paid too much.
Perhaps the list should in itself have all the data - then one manually enters date of start membership and it corrects the end date 365 days forward.
We need a simpler solution that works better in practice, im sorry....... but ill pay you for your efforts. .