add concatenated cell to list preferably without vba

[excellence]

I have a spreadsheet with a list a15:a600 , each cell contains 5 letters conditioanlaly formatted to highlight duplicates. In cell n15, I have the following =E15&F15&G15&H15&I15 where each of these cells contains a letter so the end result in n15 might be AHRUE. I would like to automatically add this (AHRUE) to the list a15:a600 (which is filled partially, but will not exceed a600), where it would add to the list, highlight if duplicate and go to to the next cell down and not be eliminated once the next set of letters are entered

Perhaps, conditional formatting is not the way to go?

Thanks

 

[excellence]

It looks to my remedial read of this, is that VBA may be necessary to achieve the result I want. So n15 text result would be added to the next empty cell in a15:a600 and highlight it if it is a duplicate of anything above it. The new entry from n15 would be entered in a15:a600 once cell n15 is entered.

Hope this is clear.

 

[excellence]

I got something close, but wonder why n15 has a moving border after macro is run, and is there a way to trigger the macro when n15 is entered..selection goes from n15 to n16? (pressing enter key)

Sub macrooo()
Range("N15").Select
    Selection.Copy
    
With ActiveSheet
Set currentcell = .Cells(.Rows.Count, "d").End(xlUp)
If IsEmpty(currentcell) Then
'do nothing
Else

currentcell.Offset(1, 0).Select

Selection.PasteSpecial Paste:=xlPasteValues

End If

End With


End Sub