It seems that others have asked different iterations of this question on this
board, but when trying to implement the solutions given within these posts,
it doesn't seem to fit my purposes.

I am trying to create a VLOOKUP function for two values that are returned
from two different drop boxes -- one dropbox is for the year, the other is
for the quarter. These dropboxes have linked cells, A1 and B1, so that when
two values are chosen (say, 2005 and Q1), A1 and B1 show "2005" and "Q1",
respectively.

Lower down in the sheet, I have a simple table of data with three columns.
The first, B50:B56, contains the year (2005, 2006, etc.). The second,
C50:C65, contains the associated Quarter (Q1, Q2, etc.). The third column,
D50:D65 holds the monthly period (Jan-Mar 05, Apr-Jun 05, etc.).

This creates some duplication of data in the first to columns, as such:

COL B COL C COL D
2005 Q1 Jan-Mar 05
2005 Q2 Apr-Jun 05
2005 Q3 Jul-Oct 05
2005 Q4 Nov-Dec 05
2006 Q1 Jan-Mar 06
.... ... ...

I would like to put a VLOOKUP formula in C1 that looks at the values
returned from the dropbox in A1 and B1, and find the corresponding row match
to these two values in D50:D65.

Many thanks in advance, and I apologize if this type of function is already
covered somewhere else on the board.