Considering that they would most likely ask you that in a social setting, say yes.
A box step in international does not exist. However, in a social setting, you can pretty much do whatever you want; like switching between styles, if you so chose.
Box steps are simple, and even if you've only been trained in international, a box step is a basic step you should have learned in your first lesson in Waltz, anyway.
Facing line of dance: LF forward, RF to side, LF closes to RF. Backing against line of dance: RF back, LF to the side, RF closes to LF. Repeat as many times as you want.