Apply IPSec policy per user, not per computer

I have a Win2000 AD Domain.

I would like to apply different IPSec policies to some computers based
on the logged on user, rather than applying the IPSec policy to the
computer regardless of the logged on user.

For example:
ComputerA
Block all Internet traffic *except* some company-approved sites (i.e.,
work related) for any user, but allow an administrator on ComputerA to
access the internet.

The bogus proxy server setting in the user config will not work for me.

Is this possible using IPSec? Is there another way to achieve this?

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