LiveUpdate via GUPs and SEPM

Scenario.

1 SEP Manager (North America, multiple subnets)
2 GUPs (one Europe, one Asia, multiple subnets)

All the subnets can reach each other.

I want to provide updates from the "local" provider.
If a client is in North America it must download content from the SEPM, if it's in Asia from the asian GUP and if it's in Europe from the european GUP.

How could I obtain this?

I have to work on both Multiple GUP and Explicit GUP but how could I include the SEPM in the equation?