Lock the Opportunity Product with validation rules once the Opportunity Stage is closed

Note:  This solution involves creating a Roll-Up Summary Field and two Validation Rules (one on Opportunity and one on Opportunity Product).

Business Case:

A Sales Manager wants to block any changes to Opportunity Line Items for all Closed Opportunities.  By adding one Roll-Up Summary Field and two Validation Rules, the Sales Manager can enforce this business policy.

To prevent create & edit to Opportunity Line Items on Closed Opportunities

Create a Validation Rule on Opportunity Product

1. Description: Prevents users from editing opportunity products after an opportunity is closed. Create the following validation rule example on opportunity products.
2. Formula: OR(ISPICKVAL(Opportunity.StageName, "Closed Won"), ISPICKVAL(Opportunity.StageName, "Closed Lost"))
3. Error Message: Opportunity Line Items cannot be created or edited because the Opportunity is closed.
4. Error Location: Top of Page

To prevent deletes to Opportunity Line Items on Closed Opportunities

Create a Validation Rule on Opportunity

Assumes that you have a custom Roll-Up Summary Field on Opportunity object called Number of Line Items, that Counts the number of Opportunity Product records associated to an Opportunity.

1.  Description: Prevents users from deleting opportunity products after an opportunity is closed. Create the following validation rule example on opportunities. It uses a custom roll-up summary field on opportunities that counts the number of   opportunity products on an opportunity

2.  Formula: AND(OR(ISPICKVAL(StageName, "Closed Won"),

ISPICKVAL(StageName, "Closed Lost")),

Number_of_Line_Items__c <

PRIORVALUE(Number_of_Line_Items__c) )

3. Error Message: Opportunity Line Items cannot be deleted because the Opportunity is closed.

4. Error Location: Top of Page