Hi:
Proc TABULATE would not call that a CONDITIONAL SUM. What you want is a subtotal or total for ALL the values of a CLASS variable. If you look at my previous examples, here:
http://support.sas.com/forums/thread.jspa?threadID=8892&tstart=0
you will see that I used the universal class variable ALL in my other posting. If you look up ALL in the TABULATE documentation, you will see why I used it to get a GRAND TOTAL at the bottom of the table:
In particular, Example 6 at this site:
http://support.sas.com/documentation/cdl/en/proc/61895/HTML/default/a002473755.htm
entitled "Summarizing Information with the Universal Class Variable ALL" should be very helpful.
And in the paper links I posted,
http://www2.sas.com/proceedings/sugi30/243-30.pdf (page 4, step 4 talks about using ALL)
http://www2.sas.com/proceedings/sugi30/258-30.pdf (page 4 also talks about ALL and ALL with generating percents)
This information is still available to you in the documentation and in the program code and the paper links previously posted.
cynthia
PS...an additional followup comment. If you want the SUM of total units sold, then you need to use the SUM statistic in your TABULATE code not the MEAN statistic.