Need help in Group Chat..???

How can we delete the conversation history from Group Chat.
When u try to press-n-hold the group name/msg, it ask us if you want to 'delete the conversation and exit the group'.

Doesnt give option to JUST delete the conversation and NOT to exit the group. I mean like Contacts list we do, but we dont have Group list from where u start the group chat. But come on Conversation TAB to just delete the conversation happened under particular group.

Pls HELP ??