Decode everything that is not defined as 'internal' or 'Web' to 'external' (oracle)
Oh... I actually read the answer before i posted the question, but didn't realize it. >&lt;

Just use the "else" variable at the end.

DECODE(supplier_id, 10000, 'IBM',
                10001, 'Microsoft',
                10002, 'Hewlett Packard',
                'Gateway')


the last variable 'Gateway' is assigned to everything that is not defined with a new value in the decode function. So in my question above i used 'External' after defining Internal and Web. 

Answer and example form here:
Oracle / PLSQL: DECODE Function | techonthenet.com