Crystal Reports with summary and sub-footer (continuation assistance required)

Currently:

However, Initially, I was instructed to calculate the average talk time..  However, what I really need is the TOTAL AVG TALK TIME for the ENTIRE group..

So I currently I'm able to calculate the avg on the change of each group..

But I need it to provide to AVG of the groups in the Footer..

Also, I don't want to display the details and just the footer.  How can I do this?  When suppresseing because I'm "WHILEPRINTINGRECORDS" everything goes to zero..  :(

Group Header:

WhilePrintingRecords;
Shared NumberVar RecCount;
Shared NumberVar DurationTotal;
RecCount := 0;
DurationTotal := 0;

Sub Report:

whileprintingrecords;
shared numbervar RecCount;
shared numbervar DurationTotal;
Local NumberVar CallDuration;

if({CallDetail.InternalNum})  >= 600 and ({CallDetail.InternalNum}) <700 then
     CallDuration := {CallDetail.Duration}
else
    CallDuration := 0;
if CallDuration > 0 then
  RecCount := RecCount + 1;
DurationTotal := DurationTotal + CallDuration;
CallDuration


Group Footer:


WhilePrintingRecords;
Shared NumberVar RecCount;
Shared NumberVar DurationTotal;

If RecCount = 0 then
    0
Else
   DurationTotal / RecCount;