I don't believe there is a method to do that - at least using the API, and non-API methods would only give you real (wall-clock) time, not CPU usage time. [I'm thinking perhaps using RDTSC to get a precise time - but it doesn't tell you if the process was "not running" during that time]
Of course, I could be wrong. I know the Linux kernel FAIRLY well, but I don't know all of it in great detail.
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Mats