Is this going to be your first undergraduate degree or do you already hold a bachelors? Just in case you have something to built on - there are a bunch of top notch Universities offering Masters in Applied Mathematics via Distance:

Columbia University: http://www.cvn.columbia.edu/app_math_MS.php

Penn State: http://www.worldcampus.psu.edu/degrees-and-certificates/appl...

University of Washington: http://www.amathonline.uw.edu/