creating geometry

Hi everyone,
I want to create a geometry which is a straight cylindrical duct with openings(ie.,circular holes) provided at some locations in the curved cylindrical wall. Basically the purpose is to simulate a fluid flow in which main flow is entering through one end of duct and leaving through the other end. The circular openings are for providing suction and blowing through some specified locations in the curved surface.
Can anyone suggest how to make openings in a duct for this purpose.

Thanks in advance!

SM Ananth