VBA Excel function that inserts the word Wier into Column o, when user selects the word Jackpot from a drop down list?

Private Sub Worksheet_SelectionChange(ByVal Target As Range)

For x = 6 To 88

If Cells(x, 14).Value = "Jackpot" Then Cells(x, 15).Value = "Winer"

    ElseIf Cells(x, 14).Value <> "High" Then Cells(x, 15).Value = " "
End If
Next x

End Sub

The issue I am having is when column O is populated by the user with any text the procedure should not overwrite the text entry.

I do not know how to write a VBA code that keeps the text entry the same and not have the procedure overwrite it.