Custom field to Display "Yes" if the Last Sales Activity of the Customer is within 30 Days.

Last Sales Activity bundle is installed in the account.

1. Navigate to Customization > Lists, Records, & Fields > Transaction Body Field.
2. Enter a Name.
3. Set Store Value to False.
4. Under the Applies To tab, select Opportunity.
5. Select Type as Free Form Text.
6. Under the Display tab, set Subtab to Main.
7. Under the Validation & Defaulting tab, set Formula to True.
8. Set the Default Value to Case When To_Number({today}-{custbody_last_sales_activity_date}) <= 30 then 'Yes' else 'No' End.
9. Click Save.