How to calculate the quantity of fixed date range？

[limingthefirst]

Hi all,

now I want to calculate the quantity of fixed date range in Column F,see below

How to write an expression in Qlikview?

This is my expression:

=sum({1<T@Date_num={'>$(=max(T@Date_num)-4)<=$(=max(T@Date_num))'}>}T@Csum*T@Price)

The problem is that all values are the same,

Please suggest.

Thanks