Count amount of unique values with multiple conditions

Hi,

I can't succeed to count the amount of unique values with multiple criteria. The columns are employee#, week, year, date and invoicing method.
Employee#: the employee# occurs so now and then double within a date. Employee# should not be counted if there is more than one unique number on unique date.
Week: The cutoff date is variable and is set on the first of may for now (Week 18). The search has to be of last month (4 weeks) on date or in the week column, so < week 18 and > week 13
Year: Year of cutoff date, so 2015.
Date: Each row has a date. As stated above there are dates with duplicate employee#'s.
Invoicing method: Should only be counted when "YES"

There has been already a similar post about this issue but I can't seem to comprehend it and apply it on my sheet.

Anyone fancy helping out?
Please find attached an Example.xlsx.


Looking forward to the responses.
Edit: Right answer is 6.
The rows that apply to the criteria are:
5 (regular)
6 (or 7 since it is a duplicate with same date)
9 ( Same employ# but seperate date)
10 (Same employ# but seperate date)
12 (Different employ# same date)
13 (Different employ# same date)