I would like to thank everybody for your help. I was able to piece together a
formula that works.

=IF((ISERROR(VLOOKUP(F16,'2000'!A1:D32,2,FALSE))), (OFFSET('2000'!A3,(MATCH(F16,'2000'!A3:A34,1)),1,1 ,1)),(VLOOKUP(F16,'2000'!A1:D32,2,FALSE)))

I used VLOOKUP with the FALSE option, which will return an error if a exact
match is not found, inside the ISERROR which will give a TRUE or FALSE
answer. That is the test for the IF function. If an exact match was not
found, I went with the MATCH/OFFSET method. If a exact match was found I just
used VLOOKUP

Now for my next question.
I have a sheets in the workbook named 1000, 2000, 3000 & 4000
the formula above refers to the 2000 sheet. At different time I need to
refer to the other sheets. Is there a way have a cell that I type in the name
of the sheet I need to refer to and the formula use that value to determine
which sheet to reference from?