drop down boxes

I have 1 drop down box that allows the selection of a
division. Then I have a macro button with code written
that takes the value from that drop down and then generates a report based on that criteria.

What I want to do is add another drop down box that will
allow me to select a particular month in addition to the
division.

I don't know how to modify my code or even if I can.
Everything I have read talks about synchronizing two combo
boxes. However, I can't find anything that illustrates
the code for 1 macro that works based on the selection in
the 2 drop down boxes.

My codes is:

Private Sub RPT1_Click()
On Error GoTo Err_RPT1_Click

Dim stDocName As String, strWhere As String
strWhere = "[Div_Desc] = '" & Forms!
[OptionListSummary]![Combo76] & "'"

stDocName = "R06 FINAL"
DoCmd.OpenReport stDocName, acPreview, , strWhere

Exit_RPT1_Click:
Exit Sub


Any ideas?
Thanks in advance.