Calculating the Duration of Months Based on a Picklist Value in Salesforce

To calculate the duration in months from a start date to today when a specific picklist value is selected, follow the steps below :

Step 1:

• Navigate to Setup > Object Manager
• Select the object where you want to add this formula field
• Click on Fields & Relationships
• Click New to create a new custom field
• Select Formula as the field type and click Next

Step 2:

• Enter a Field Label and Field Name, then select Number as the Formula Return Type
• Set the Decimal Places to 0 for whole months or as needed
• Click Next

Step 3:

• In the Formula editor, enter the following Formula

IF(
ISPICKVAL(PotentialLiability__c, "Yes"),
(YEAR(TODAY()) - YEAR(Start_Date__c)) * 12 + (MONTH(TODAY()) - MONTH(Start_Date__c)),
0)

Step 4:

• Click Next and set field level security

• Click Next and add the field to appropriate page layouts

• Click Save to complete the process

Note : For more complex requirements, such as handling multiple picklist values or including partial months in the calculation, the formula can be further customized. You may also consider using a validation rule to ensure the start date is not in the future if that's a business requirement. Remember that formula fields are calculated at runtime and do not store data, so they're ideal for this type of dynamic duration calculation.