Question: I need to understand the fine details, possibilities and pricing of Salesforce OEM model. I can't find an official link about this on salesforce and google, only link available is this 2008 pdf : <http://www.developerforce.com/tdf/2008/april/Force_ISV_Partner.pdf>

Please share any good post/article on this.

Answer: 
I recently wrote a blog post about [locking records using approval processes](http://verticalcode.wordpress.com/2012/07/26/locking-a-record-from-editing/). It is a pretty big hack, but it allows you to lock a record without having to use separate page layouts or record types. Here's how it could work:

1. Set a time-based workflow rule to update a boolean field called "Lock Record" 90 days after the Opportunity is closed.
2. Have a trigger that fires when the "Lock Record" field is checked.
3. The trigger invokes a simple approval process that when finished leaves the record locked.

Admins can unlock the record by clicking the Unlock button at the top of the page, but they can also edit the record without unlocking it.
I have used this syntax in a validation which has seemed to work well.

```
PRIORVALUE(LastModifiedDate) <> NOW()

```