limits.conf Limiting CPU

[RobinVossen]

Hello,
I have a Linux Box with Remote Access for a couple of users.
I want to limit the CPU usage for each user in a Different way.
So I found limits.conf..
The only thing you can limit there as for CPU is the maximum CPU time (minutes).
Well my Question is is there a way to limit each user to max use 500Mhz for example? or 30% of CPU?
Or how can I calculate how much Minutes that should be?

Thanks.

[RobinVossen]

Hello, bin a long time.
Lets put this back on the top.
Since I googled alot. and I still cant find away..

Cheers,
Robin