How to Create a Saved Search for System Notes

Hi guys,

I was wondering if it is possible to have a Formula Date field for the system notes only with the following criteria:

System Noted: Field = 'Sent to Vendor'

System Noted: Type='Change'

System Noted: New Value= (not sure, this is a check box field so either Y/N or T/F - please advise)

System Noted: Date

I tried to create the following but it did not work, any ideas what I am missing?

CASE WHEN {systemnotes.type}='Change' AND {systemnotes.field}='Sent to Vendor' AND {systemnotes.newvalue}='Y' THEN {systemnotes.date} END

Thank you