Are you working with NAV 2009 or 2013?
With "Add code to get the same" you probably meant to add content to codeunit 1, functions GetSystemIndicator and table 79, GetSystemIndicator - right?
At least that would have been the way I'd tried it.
But as you've already stated, the system indicator is built to be loaded once per CompanyOpen because its values normally do not change in the meantime. GetSystemIndicator in codeunit 1 is not called by any other normal C/AL function.
I do not see any way to update the system indicator unless you'd restart your client :-/
Maybe - but I am not a C# geek - you could search in the C# code for a reference of GetSystemIndicator and call it again using the DotNet interop?