dcorrea - Yes, you should be able to do this using QoS maps on the NetVanta 3458. The summary below explains at a high level what will need to be configured on the NetVanta 3458:
You will need to create a QoS map that will match traffic being sourced from the server. The QoS map will then shape the matching traffic to the 4Mbps throughput the customer desires. This QoS map will need to be applied to the Ethernet WAN interface so that the traffic throughput is restricted for the server.
Further details on QoS and an example similar to what I explained above can be found in the link provided below. Example #4 should be the closest implementation to what you are looking to do.
Please do not hesitate to let us know if you have any further questions or issues in setting this up.
Thanks for the help, I will work on this.