Hi,
I would distinguish your question to two cases:
1. Current Concurrent Calls
The calls that are happening righ now. In this case, CDRs are not usable, they inform only about past/disconnected calls. CUCM does not have a list of such calls either. However you can collect such information by using TAPI/JTAPI, but it is not a trivial task for few days. But there are some 3rd party utilitied/software that can do that for you (e.g. I lead a development of a product that can do that - www.2ring.com/newjuice).
2. Calls that are already Disconnected
In this case, you can use the CDRs to see the such call history but, again, CUCM will not sutisfied you. You can try Cisco CDR Analysis and Reporting, but do not expect much. I would say thay for this you need to check any other 3rd party solution - CDR analysis tools, and or Call Accounting systems, they usually can create report for your needs, if they do not have it already. We gave one such product as well and you can find more here:
https://marketplace.cisco.com/catalog/search?utf8=✓&search%5Bq%5D=accounting&commit=Search+Solutions+Catalog&search%5Btechnology_category_ids%5D=-1%2C23%2C24%2C25%2C26%2C27%2C28%2C29%2C30%2C31%2C32%2C33%2C34%2C35%2C36%2C37%2C38%2C39%2C40%2C41%2C42%2C...
I hope this helps.
Jiri
