I'm sure this is really simple, but i'm crap at excel 
say i've got two columns like below:
A1 B1
1 1
2 2
3 4
4 5
5 6
6 7
What i want is a forumla to sort and then display the numbers that is in one column but not the other column, so in this case number 3
Hope that makes some sense, i've got excel tunnel vision at the moment lol
Anyone got any ideas? This is doing my head in now!

say i've got two columns like below:
A1 B1
1 1
2 2
3 4
4 5
5 6
6 7
What i want is a forumla to sort and then display the numbers that is in one column but not the other column, so in this case number 3
Hope that makes some sense, i've got excel tunnel vision at the moment lol
Anyone got any ideas? This is doing my head in now!