How to copy a value to an auto filtered column and only paste to the filtered rows in VBA

Hello Everyone,
I am very new to VBA. I have a requirement from a client that I have to complete by Monday. I have a spreadsheet that could possibly have over 20k rows in it and approximately 20 or so columns. They want to be able to use the auto filter for any of the 20 columns to get the rows that they want to show on the spreadsheet. Once that is done they want to apply a factor or apply a date that the user will enter into another range on the sheet to ONLY the visible rows and into one specific color coded column. So I can't do a regular copy paste because it will paste the factor or date entry over all 20k of the rows even if they are not showing in the filter. If there is anyone who could assist me I would be grateful. I have been working on this for a while and It is due Monday.