Radius Server and Ldap Server

Hello all, I am trying to set up a radius server to perform authentication for wifi login against the user with password database in LDAP. I have no right to get the password back from LDAP, and the only reply information from LDAP server is the I login in success. However, I need to login wifi by a user name and password stored in LDAP server, without the reply password from LDAP, how can the radius server check whether the password I have provided is correct. I have tried many ways, but none of them work. I need help from you. Thanks. Best Regards Li