Ok, this hack consists of :
- add a 'thank you' button in the showthread, so instead of having 20 replies saying 'thank you', each member click this button, and their name is automatically added to a post displayed in 2nd position which shows the total list of members who clicked this button
That's why I'm asking boofo whick kind of datas he wants to add (date ...) and I could take some other good ideas suggested by other members before begining it