Alter properties of a menu item in Eclipse Plugin?

Question

I am trying to modify the behaviour of File -> Refresh in the menu bar of my Eclispe plugin. I am effectively trying to override the activeWhen behaviour of the "org.eclipse.ui.file.refresh" command, so that it is always active.

There seems to be plenty of information on creating these menu items but very little on overriding them, any ideas?

Code I tried was:

ICommandService commandService = (ICommandService
     PlatformUI.getWorkbench().getService(ICommandService.class);
Command command = commandService.getCommand("com.detica.netreveal.builder.config");
command.setEnabled(true);

But this doesn't do the trick