ExcelBanter - pivot table excel

I have two worksheets set up. The first is an overall database recording the
names and types of a set of mechanical units, and tallies the total number of
each type of unit. This database does not change. I have another worksheet
which is a continuously growing record of maintenance on various units that
includes the date, the location of the unit by zone, and other bits of info.
I've generated a pivot table from this second worksheet and it is working
well. What I would like to do is take the grand total column/row created with
each pivot table and create another column/row along with it that calculates
what percentage the grand total is of the total number of units. For example,
if the grand total tells me that on a given day, this x number of units of a
specific type were repaired, the x number being the grand total, I want to
know what percent of the total number of units of that type (which I can get
from the first, non-changing database) is x? I know that I can use
GETPIVOTDATA to do this in a specific cell, but I'd rather be able to allow
the data to follow the pivot table in the same manner that the Grand Total
calculation does, to be a part of the pivot table and give the percentage of
whatever the data happens to be as I change the fields. Is there any way I
can do this? Thanks for any help you can give me!