Suggest that the time period be defined clearly as a particular "month-year",
for eg: Dec08
rather than just the month

Assuming col B contains real dates
you could use something like this:
=SUMPRODUCT((TEXT(B2:B1000,"mmmyy")="Dec08")*(A2:A 1000="Product A"),C2:C1000)

Adapt the ranges to suit the smallest max data extent
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Max
Singapore
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xdemechanik
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"JeffK" wrote:
I have a spreadsheet that consists of 3 columns and infinite rows. Column A
= Product type (A,B or C), Column B = Date (ddmmmyy), Column C = $ amount. I
used SUMIF to calculate the total $ sold of Product A but I want to now
stipulate a time frame (eg month of December). The data will continue to be
added to, so I want the total to adjust as new entries are added.