i have problem in VLOOKUP function

When using Vlookup
Example:

A B
1 5
2 6
3 7
4 8
5 9
If I use vlookup(2.7,a,2,true) I get 6. but i need the average between 6 and 7 (i.e. (6+7)/2=6.5)
Can this be done?
Thank you.

in cell a1 to b6 I have your table.
in cell b9 I enter my value
in cell b10 I calculate my exact value, using rounddown. =ROUNDDOWN(B9;0)

In cell c9 I use vlookup. In this case I have to find vlookup of 2 + vlookup of 3 /2

=(VLOOKUP(B10;A2:B6;2;FALSE)+VLOOKUP(B10+1;A2:B6;2;FALSE))/2


In summary, you can combine these two step in one.
In cell c9 you put this formula:
=(VLOOKUP(ROUNDDOWN(B9;0);A2:B6;2;FALSE)+VLOOKUP(ROUNDUP(B9;0);A2:B6;2;FALSE))/2

very good
thank you very much