First, just for the record, there is no Access object called a
"Subreport"... there is a Control called a Subreport Control, into which you
can embed a Form or another Report.

And, since you cannot "pull up" a Subreport Control without opening the
Report in which it resides, I am guessing you mean you are independently
opening the same Report that is embedded in a Subreport Control in another
Report. But still...

As you haven't explained what data you have, what the RecordSources of the
two Reports are, how you are determining the totals, whether you are relying
on the total calculated in the Report imbedded in the Subreport Control to
set the total in the main Report, or calculating it separately -- e.g., you
told us little about what you are doing. Thus it is not very likely that
anyone can tell you what is wrong about it.

You have the Database and all this information at hand... but unless you
convey it to us, we don't have much to go on. Provide some specific
information and perhaps someone can suggest a solution.

I'll even guess that one solution might be to set the ControlSource of the
Total in the main Report to a DSum domain aggregate function -- if you were
counting on the calculation in the Report in the Subreport Control being
transferred in some way to the main Report.  The DSum might be a good deal
simpler.

 Larry Linson
 Microsoft Access MVP