Editing a shared document that has some read-only capabiities
 

We have an excel document where all of the columns, except for three, have
been locked down. We password protected the spreadsheet and then shared it.
Most cells are read only, but there are places that certain users need to
click and type into. Somehow the columns that were unlocked have become read
only. As I am the only one with a password and I have not opened the document
I'm not sure how this happened...

This type of scenario where a document needs to be shared but the integrity
of the data needs to remain occurs often and I've run out of Excel tricks.
How can we have a shared document with some read-only capabilities that can
also be selectively edited?