I am trying to lookup values from a work book that has the same worksheet for
different months. The first column of these worksheets contains an
identifying number. I named the first column of these sheets the month name
and the full lookup array the month with the number 1 on the end. I used the
following array formula to lookup the value in column three of the different
lookup arrays for a cell D2 containing an identifiable number.
{=IF(OR(D2=JANUARY),VLOOKUP(D2, JANUARY1,3, FALSE), IF(OR(D2=FEBRUARY),
VLOOKUP(D2, FEBRUARY1,3,FALSE), IF(OR(D2=MARCH),VLOOKUP(D2, MARCH1,3,FALSE),
"NOT VALID")))}

I would like to have this formula hold true for the entire year, but I can
only nest 7 if statements. I think I need to write a select case custom
function, but I do not know the syntax to compare the function value to the
different months. Here is a code example of what I want to do.

FUNCTION SPECLOOKUP(ID#)
SELECT CASE
CASE ID# IS WITHIN JANUARY
SPECLOOKUP = WORKSHEETFUNCTION.VLOOKUP(ID#,JANUARY1,3,FALSE)
AND SO ON.
END SELECT
END FUNCTION
Can someone tell me how to write the cases correctly?


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Thanks
R. Patterson