Append query adding text with null value in the primary key

[AAbrams]

I have an inherited issue, and I appreciate any help anyone can offer.

I import a table with seven fields, of which one is PRICE, as a new table
from a *.csv file. PRICE is the text of a sticker to go on the retail
package.

I then have to append this new set of data to an existing table with six
fields. Of those six fields, FIVE are defined as the primary key, including
the PRICE field.

This PRICE field can have numbers (.99, 2.19, etc.), text (2/$1.00, etc.),
or be null. THe specification currently brings this is as a text field.
The problem comes when I try to append to the existing table. Because of
the null values, the append kicks out records as key violations, but I can't
convert to a number and use the N0 function to assign values to the null
fields.

I cannot change the data as it comes in, nor can I get values assigned where
there are none - those packages get no label.

How can I get the append to work with nulls in the primary key? Is there a
transfomation or function I can add which will allow this to work, yet
maintain the text of those fields which are text (the most troubling are
fields like "2/.99", where Access tries to perform the operation)?

Thanks for any help,

Alan