How many outside calls can we make in a conference call with CME and CCM ?
Before Cisco Unified CME 4.1, support for conferencing is limited to three-party ad hoc conference calls using a G.711 codec.
In Cisco Unified CME 4.1 and later versions, multi-party ad hoc and MeetMe conferences allow more than three parties.
From this excellent CME doc;
Cisco Unified Communications Manager Express System Administrator Guide - Configuring Conferencing
Hope this helps!