[Excel 2003] Read-only password : need second hash ?

Hello,

Just succeed in colliding a excel 2003 password with -m 9710 then -m 9720. (oldoffice$0)

This gave me a working password to open the document.
To modify it, Excel ask me another password (the first one does not work).

For this second password, I guess we need a second hash, how to extract it ?