You can also use PhoneLib from
www.mitan.co.uk. PhoneLib is part of the PhoneCalc Suite, which provides a lot of call-center calculation function free in demo mode (no time limit).
PhoneLib is a DLL, and comes with simple instructions for use with Excel (or
VB if you wish). Erlang-C is provided. If you buy a licence then you also get Erlang-C with fractional agents and Mitan-C with interg and fractional agents.
A new version of PhoneLib (and the rest of PhoneCalc Suite) is planned for release in the next few months, which will add a number of other queueing models (such as Erlang-C with limited queue size) to PhoneLib.
There re no upgrade charges to Mitan products, so if you buy now the upgrade invloves no charges.