never matching numbers

Hello all,
If i have 16 numbers in col A,
what i want to do is in cols C,D show the numbers 8 in each column,but the numbers can never match.what i mean if number 7 is in C2 it can not appear again in either column until i hit F9.
Then in cols E,F do the same for numbers 1 to 8.

I have attach a sample if you like to view it.Thanks