Translation of auffüllen

After next week, I will tutor the Mr. Zillmay from the language lab in Los Angeles, he is currently in the states. The lesson will take place in LA, but it may be held no earlier than mid-February.
I've also looked at the interface, and found it a good idea to include the colloquial option. Would it be very complicated to add the most important regional check box, like Spain, South America or Central America?
I've actually found Vocabulix only because I could not conjugate an English word and then I suddenly was there: learning vocabulary, and meeting friends makes so much fun ...