Search: Sales Orders within 5 Days of a Phone Call (Activity)

Hi -
I'm trying to create a search where I can see that within 5 days of a Phone Call logged on a customer record, the customer places a Sales Order.

I have tried a Transaction Search (SO)  And I tried a Customer Search.  I'm getting no results.

Transaction Search:  Type = SO, Main Line = True, Activity.Activity Type = Phone Call, and Formula = YES :  DECODE({trandate},{activity.date}, 'YES',  {activity.date}+1, 'YES',{activity.date}+2, 'YES',{activity.date}+3, 'YES',{activity.date}+4, 'YES',{activity.date}+5, 'YES','NO' )

Customer Search - Basically the same, but
Transaction (Customer) : Type = Sales Order, Activity.Activity Type = Phone Call, and Formula = YES :  DECODE({custbody2.trandate},{activity.date}, 'YES',  {activity.date}+1, 'YES',{activity.date}+2, 'YES',{activity.date}+3, 'YES',{activity.date}+4, 'YES',{activity.date}+5, 'YES','NO' )