I did not cross the border! First I spent 4 weeks in Argentina. I came by regular bus from Iguazu to Posadas, Resistencia then San Miguel de Tucuman and North West of the country.
4 years later I visited Chile in a separate trip.
A solution for you is to cross twice the border at the same place: Mendoza- Santiago and then back in Mendoza.
... or you can also consider the possibility to do Santiago - La Serena - San Pedro - Salta and surroundings - Tupiza, and there you are in Bolivia !
[ Edit: Edited on 05-Nov-2014, at 10:42 by Alain13 ]