According to Wikipedia, mice and men diverged 75 million years ago and then we had the major KT event 10 million years later.
http://www.ucmp.berkeley.edu/diapsids/extinction.html
http://en.wikipedia.org/wiki/Dinosaur_extinction
http://en.wikipedia.org/wiki/Timeline_of_evolution#_note-20
http://en.wikipedia.org/wiki/Timeline_of_evolution#_ref-20