Folks,

Bruce, your solution was elegant, but I'm such a poor programmer that I need SAS to talk to me all the time or I mess up. So I kind of slid around Henry's suggestion:

compute before subj; if subjenr or subjsch then do; pctdevenr=devenrsum/subjenr; pctdevsch=devschsum/subjsch; pctlowenr=lowenrsum/subjenr; pctlowsch=lowschsum/subjsch; pctupenr=upenrsum/subjenr; pctupsch=upschsum/subjsch; pctprenr=prenrsum/subjenr; pctprsch=prsch.sum/subjsch; pctgrenr=grenrsum/subjenr; pctgrsch=grschsum/subjsch; pcttotenr=totenr.sum/subjenr; pcttotsch=sch.sum/subjsch; end; endcomp;

This worked. It could get a little hairy if there were, say 500 variables that might be subtrahends in the divisions. I still wonder if there's some elegant way to tell SAS not to divide by a missing value, which you could use when you know you'll have missing values in the variables you may have to divide by.

Pat