You can use Group Policy to configure the Update Source Location:
http://blogs.technet.com/b/odsupport/archive/2014/04/28/new-group-policies-introduced-with-the-april-2014-update-of-office-2013-click-to-run.aspx
e.g.: for computers located in the corporate network, use this to configure the update source as your on-premises repository, and, for computers which are located outside your corporate network, leave the defaults in place/configure for MSFT CDN.
Or perhaps another alternative might be this: if you have content-caching appliances/services available within your corporate network/DMZ/edge, those content-caches could serve the MSFT CDN content efficiently to your corporate computers (in this case, all
of your computers could be configured as default for MSFT CDN. This would mean that laptops which may come-and-go could "automatically" reach the most effective/efficient "copy" of the MSFT content)
Another alternative might be to consider some "clever" internal DNS/proxy logic, again this would allow you to leave the computers configured for MSFT CDN default and allow your network/DNS/proxy to resolve "internal" requests to your
on-premises repository.
[just a few thoughts...]