Counting # Of Unique Items In A 12 Month Period (Table)

Hi guys,

I had my earlier issue solved by a forum member, but i met another big problem with counting unique items.

We have a problem that requires us to count the number of customers that purchase our equipments, within a period of 12 months. There are customers who come back on a regular monthly basis, and we want to count that as only ONE customer. We need to count the NEW customers. Repeated customers are not supposed to be counted within the 12 month period.

I have uploaded a sample workbook. Please help me look into this difficult one.

Thank you guys for your expert help.

regards,
LIM