Crystal Reports - Calculated Member Drops from Rep...

I have a calculated member with a code that calculates the total values of the previous 10 rows.  However, sometimes there are less than 10 rows, because there was no data at that time.  When this happens, the calculated member "drops" from the report.  How can I change my code to compensate for "null" or "missing" rows?

Thanks for your help!

Here is my current code for the Calculated Member:

if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -1, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -2, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -3, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -4, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -5, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -6, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -7, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -8, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -9, CurrentColumnIndex ,1 ) +
if GridLabelAt ("Scheduling_Locations.Description",CurrentRowIndex) startswith ["Total"] then GridValueAt (CurrentRowIndex -10, CurrentColumnIndex ,1 )