Poss Table Array or Lookup Feature

[Gassiusmax]

Hi I have a query and hope you all can help.

Sheet A
A B
1 N2 1 formula
2 N2 2 formula
3 N2 1 formula
4 N2 3 formula

I am trying to put a formula in B1 to lookup data in sheet B that matches A1, but where A1 and A3 have the same info the result is duplicated thorugh a normal vlookup. Is their anyway I can stop it duplicating and either give an error message of even better if their is a second entry in the other table to reveal that one.

For example
sheet one is as above and sheet two is below

Sheet B
A B
1 N2 1 Dave
2 N2 2 Michael
3 N2 1 Tom
4 N2 3 Perry

a vlookup written as Vlookup(A1,SHEET2!A1:B4,2,FALSE

Will show B1 and B3 as Dave, what I am trying to achieve is B1 is Dave and then B3 is Tom

Thanks if anyone can