Shortcode for all mulisite sites

i need a plugin, where i can manage tekst/image from the main wpmu.

Ex:
sub1.site.com haves a tag/code [example]
sub2.site.com haves a tag/code [example]
sub3.site.com haves a tag/code [example]

And on the main site is [example] defined as “hello World”, when i change the text “hello Netherlands”, i want it to change on all site. (sub1.site.com, sub2.site.com, sub3.site.com)

Does someone know a pluging or a trick to do this?