The approach I would take would be to create the pivot  table from rows  1 to,
say, 400. then when the pivot table  is refreshed it will take into account
any new rows added. It may have an entry for the blanks but generally that
does not matter.

I can add  one more suggestion. Create a dynamically named range for the
data area. Dynamically named ranges  are created  using offset function. I am
giving a brief example  below

· To Expand the named range Down to as Many Rows as There are Numeric
and Text Entries.

a. Define a name (Insert -> Name -> Define). Let us assume you give the
name 'Test'

b.In the *Refers to* box type: *=OFFSET($A$1,0,0,COUNTA($A$1:$A$400),2)*

c. Your A column  entry is assumed to start at A1 and expand upto A400.
(These values can vary ofcourse)

d. After defining the name Test, create pivot  table.

e. In pivot table  denition, instead of address for the area, give the name
Test

The pivot data  area will become dynamically defined and the refreshing will
take place with newly added data automatically.