Try this,

=SUMPRODUCT((A1:A100=DATE(YEAR(TODAY()), MONTH(TODAY())-6,
DAY(TODAY())))*(B1:B100="MD902")*(C1:C100))

Change A1:A100 etc to match your range
You might also consider referring to a cell for MD902 instead of having the
search string within the formula.

Mike

"AOU" wrote:

I have a spreadsheet as follows:
A B C
date MD902 40
date MD902 30
date BO105 20
date BO105 10
and so on between rows 6 to 20006

I would like to be able to produce the total of column 'C' for the last 6
month of MD902 and BO105.
--
AOU