set time as non-admin user

we tried to run our system under a non-admin user to prevent clients from
installing programs. We found out we could not correct the system time from
our program when we do that. Is there a way to work around this? The o/s is
windows 2000 or xp. All we have is a workgroup and the program just calls the
setlocaltime function.
Any help will be appreciated, thanks.