OK, that simplifies things.
So, the parameters are:

User inputs starting/ending dates.
Macro reads data  and stores in Dictionary using date as key.
Starting with starting date, the date is entered in column A,
and if data exists in Dictionary, it is entered in B-??
Sound right?

How many columns contain data?
What kind of data? strictly numeric? Alpha-numeric?
what about special characters? underscores(_), colon(:),
pipe(|)??