shared variables will do the same as running total but you do all the work in formulas. usually in groups of 3, reset, increment, display, start with the easiest:
reset (usually in a group header)
shared numbervar x;
x:=0;
"" // will hide the reset
increment (usually in details)
shared numbervar x;
if some condition then
x := x + {table.field};
"" //again hides the increment from displaying on the report.
display (usually in a group footer)
shared numbervar x;
x
HTH