Networking :: Control Bandwidth Access With Squid - Allow Certain IPs To Have Higher Bandwidth Access?

We have a sipmle office network set up that we also use use to connect to the internet, however of late the number of users has increased thus slowing internet access. Bandwidth upgrade is not an option thus i have to do bandwidth shaping on our linux router. The question is how do set the squid configs to allow certain IP's range a certain percentage bandwidtheg 60% and furthe divide the rest. Alternatively how can allow certain IPs to have higher bandwidth access.