Using gridview datakeynames with muliple keys question

[needin4mation]

I have a master/detail setup with two gridviews. In the detail table I
have a primary key and a related key from the master table. I want to
hide both keys. I can do that easily with the primary. If I set
visible=false on the other key, I can't update the database because
nothing is posted back (I know that changed in 2.0).

If I put multiple keys in the datakeynames="key1, key2," how can I get
to key2 to update the row?

The primary key, key1 here, uses
OldValuesParameterFormatString="original_{0}" in the objectdatasource.
What do I do for the second key to get it in the database?

Thank you for any help.