group variable

Hy all I would like to use the name of the group a user is member of to update the check item list. I though using unlang to do so, and an update directive but icannot find the variable name (if any) to use for the name of the group. I have "%{Group}" "%{Group-Name}" "%{SQL-GROUP}" but no success: expansions always gives me an empty string. The groups are stored in MySQL database. the update directive is at the end of the autorize section.... Does anyone knows how to refer to the group?