Help in selecting variable range while creating macro

[Nayaz79]

I need a help in selecting range while creating a macros. My requirement is I have recorded a macro which should work in any selected column the range it should select is from the previous column last data row to the top. In the below macro the problem is it is selecting the entire column and data is filled in the entire column from K3:K1048576. Please help me to fix this and it should work in any column.

Sub Macro3()
'
' Macro3 Macro
'
' Keyboard Shortcut: Ctrl+l
'
    ActiveCell.FormulaR1C1 = "=RC[-1]/RC7"
    ActiveCell.Select
    Selection.NumberFormat = "0%"
    Selection.FormatConditions.Add Type:=xlCellValue, Operator:=xlLess, _
        Formula1:="=0.75"
    Selection.FormatConditions(Selection.FormatConditions.Count).SetFirstPriority
    With Selection.FormatConditions(1).Font
        .Color = -16383844
        .TintAndShade = 0
    End With
    Selection.FormatConditions(1).StopIfTrue = False
    Selection.Copy
    ActiveCell.Select
    Range(Selection, Selection.End(xlDown)).Select
    ActiveSheet.Paste
End Sub