Here is a solution that produces the following results....
![p.png p.png](/t5/image/serverpage/image-id/539iBCC4DDF22C388DAF/image-size/large?v=v2&px=999)
Where cell labelled 'A*B*C' has a FormCalc calculate event as depicted by row[0], below
// form1.page1.subform1.table.row[0].sum::calculate - (FormCalc, client)
var sum = row[0].a + row[0].b + row[0].c
if (sum == 0) then
0
else
Max(row[0].a,1) * Max(row[0].b,1) * Max(row[0].c,1)
endif
![p1.png p1.png](/t5/image/serverpage/image-id/540i7DAEE18BD812C5B4/image-size/large?v=v2&px=999)
Steve