Assuming PDT1 is in B2:D2, PDT2 is in F2:H2. Then, in J2 you can put
your figure for PDT1:

=SUMPRODUCT((B2:D2<"")*(F2:H2<"")*(B2:D2-F2:H2))

HTH
Kostis Vezerides

sarah wrote:
I have this whole spreadsheet which i had to subtracted sum of YEAR 2 figures
from sum of YEAR 1 in the corresponding period.

For example:
Pdt 1 Result = (Year 2 M3+M2)-(Year 1 M3+M2)
Pdt 2 Result = (Year 2 M3)-(Year 1 M3)


YEAR 2 YEAR 1
M3 M2 M1 M3 M2 M1

PDT 1 200 200 400 400 400

PDT 2 400 500 500 500
PDT 3 100 100 100 200

PDT 4 500 500 200 200 200
PDT 5 100 100 100 100


Is there anyway i can do this effectively?


--
sarah