Macro to copy/paste values to new row OR overwrite existing row

Just signed up for this and having trouble finding a solution to the challenge I have at hand. I'm hoping someone can help, and I apologize if there's already been a solution posted, but I wasn't able to find it, so here goes!

I have a weekly report that will be used to collect data for an asset, and I have built a simple macro to copy & paste the values of that data to a new row on a separate sheet. The purpose is to keep a log of weekly stats so we can identify trends. The macro is working as intended, but I want to improve it to be able to account for a certain element of human error.

It is reasonable to assume that the people filling out the weekly report will at one point or another (or maybe more often than that) click the "Finalize Report" button which cues the macro to publish the data to a new row, then shortly thereafter realize that they need to correct some data and "re-finalize", thus re-publishing the data to a new row. This would result in multiple rows of data for the same date. The sheet where this is happening is password protected by design so that it can't be altered. I would like to redesign the macro to paste the data to a new row ONLY if the value in column A (the date of the report) is unique, and if the value in column A already exists in the list of data, then overwrite that row with the new data.

This seems like something that's possible, but I'm fairly new to macros, so I could use some help!

Here's the macro code as-is, which simply copies and pastes the values to a new row:

Sub FinalizeReport()
'
' FinalizeReport Macro
'

'
    Sheets("Cumulative Stats").Select
    ActiveSheet.Unprotect Password:="29401"
    Range("A2:AD2").Select
    Selection.Copy
    Range("A" & Rows.Count).End(xlUp).Offset(1).Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Sheets("Cumulative Stats").Select
    Application.CutCopyMode = False
    ActiveSheet.Protect Password:="29401"
    Sheets("Weekly Report").Select
End Sub