How do I create a formula that will refresh weekly
 

I hope someone can help me with this question, I have created an access DB to produce all invoice and quote dollare for a specific brand. I summarized the information into a pivot table. I added a custom filter to show only those customers with sales greater than or equal to $750. What formula can I use to capture the number of customers that meet this threshold on a weekly basis?


MgrEmail Customer Name 2013
FRANCISCAN MEDICAL GROUP $750
ST. JOHN HEALTH SYSTEM $800
GIFFORD MEDICAL CENTER $900
Total $2,450
BRIDGESTONE/DES MOINES $750
Total $750
CORPORATE EXECUTIVE BOARD $750
MEADWESTVACO $800
ADVISORY BOARD COMPANY $900
BOOZ AND COMPANY $950
DUNBAR ARMORED INC $945
RADIO ONE INC $899
Total $5,244
PHH CORPORATION $800
SODEXO $841
MENTOR NETWORK $954
HALLER ENTERPRISES INC $999
MCCORMICK AND COMPANY INC $12,546
MIDDLEBURG BANK $23,665
Total $39,805
QLOGIC CORPORATION $485,445
Total $485,445
NATIONAL INSTITUTES OF HEALTH $59,746
Total $59,746