I am not a running totals guru, I am sure that there is a way. DBlank is the master of the running total. I use shared variables...

they're not too hard, the quick primer:
the tend to come in groups of 3 (and basically duplicate running totals:

reset formula (usually in the group header)
shared numbervar cnt :=0;
"" //hides the 0

display formula (usually in the group footer)
shared numbervar cnt;

increment formula (usually in details)
shared numbervar cnt;

if (some logic) then
cnt := cnt + 1;

"" //again hides the running count


HTH