Have a look at this thread. via Bob Umlas.

From: BobUmlas ()
Subject: Re: Vlookup also
View: Complete Thread (3 articles)
Original Format
Newsgroups: microsoft.public.excel.worksheetfunctions
Date: 1999/07/12

Set up the table like this (5 rows, 2 columns)
0  F
60 D
70 C
80 B
90 A
Name these 5r x 2c "Grades" (Not required, but good practice).
To find someone's grade using the value from column K, enter
=VLOOKUP(K2,Grades,2)
Where K2 is one of the grades. The 2 in the formula says to return the value
from the 2nd column of the table called "Grades".

http://www.google.com/groups?q=vlookup+grade+group:*excel&start=10&hl=en&lr=&ie=
UTF-8&oe=UTF-8&c2coff=1&selm=OXMN5GNz%23GA.52%40cpmsnbbsa05&rnum=19

Regards,
Kevin

In say, Sheet1, set-up a grade table in A2:B6
------------------
0 F
50 D
70 C
80 B
90 A

The above table presumes a slight tweak to the grade criteria, i.e.:

A: >=90
B: >=80 to <90
C: >=70 to <80
D: >=50 to <70
F: <50

In Sheet2, assume the marks are in col A, A2 down
------------
Put in B2: =VLOOKUP(A2,Sheet1!$A$2:$B$6,2,TRUE)
Copy B2 down as many rows as there are data in col A

Col B will return the grades according to the grade criteria specified