Security considerations for partially shared password databases
What you are looking for is an authentication and access service on top of a password management system. There are a couple of solutions in this space, but they are corporate and expensive:


http://www.liebsoft.com/privileged_identity_management/ 
http://www.cyber-ark.com/digital-vault-products/pim-suite/index.asp
http://www.netwrix.com/privileged_password_management.html
There are about 10 other companies and products in this space.


There are also some web based versions of keepass which may fit your needs, but then you'll need to secure the HTTPS, etc.


http://sourceforge.net/projects/webkeepass/