I think you actually have two problems. The first is that Eclipse doesn't allow the workspace to change without your knowledge. Normally this is preferred, so you have a stable work environment. So you would have to refresh the workspace to see changed files.
The second is that it sounds like you are committing changes to CVS outside of Eclipse? If you commit and update from Eclipse, you don't have to refresh the workspace.
And finally, is this update supposed to retrieve changes by other users? If so, you will always have to perform the update to get the changes. You should do this from Eclipse for simplicity.
You can follow these instructions to add the CVS plugin to Eclipse, if it's not already there. http://www.eclipse.org/eclipse/platform-cvs/