Basically, I would like to convert some numbers.

I would always like to convert:-

1 to 6
2 to 5
3 to 4
4 to 3
else = 0.5


If I had the following numbers displayed in cells A1:A10

1
2
3
4
5
6
7
8
9
10

How could I get them displayed as:-

6
5
4
3
0.5
0.5
0.5
0.5
0.5
0.5

in cells B2:B10?

They would not normally be in numerical order as above.

Would I require a LOOKUP?

TIA