Fre, I'm probably misunderstanding your need. You posted this in the programming forum, but it isn't obvious to me that you need a VBA program for it. Let me rephrase this and see what I'm getting wrong. If you were doing this manually, rather than in VBA, your steps would go like this:

0) There exists a file Input.xlsx.

1) You open Input.xlsx (I know, it's supposed to be a copy; bear with me a minute.)

2) You do whatever you want to Input.xlsx—filter, change the value in the date_of_start column, whatever you like.

3) You save the results to Lookup.xlsx, and also save it to Input.xlsx.

Now the changes you made are both in Lookup and in Input. Isn't that what you wanted? I figure it isn't...but what am I missing?