COUNTIFs with 2 or more criteria

Hi all, wondered if you could help. On the attached spread sheet in C4 of the values tab i need to count the number of unique values (no duplicates) in col F of the date drop tab based on the date in D4 looking at the dates in col H of the date drop tab.

I've probably not best expalined but the knida formula i'm after is

For C4 Count the number of unique referances (no duplicates) in col d data drop if the date in col H date drop is less than the date in D4

For C5 Count the number of unique referances in col d data drop if the date in col H data drop is equal to or greater than the date in D5 but less less than the date in E5

I take it i will then be able to copy down to get the rest?