RES: Stuck with exec script from radgroupreply sql table

I want to set a dynamic "Session-Timeout" for certain groups. For testing purposes I created a TESTGROUP in the database table radgroupreply with an entry like this:

id GroupName Attribute Value op 263 TESTGROUP Session-Timeout `%{exec:/var/skripte/test.sh}` ==

Try to use a mysql procedure to return this value in the stand query.