n=300
a = range("L2:L300")
for i = 1 to n
If Cells(a, 12) = 4 Then cells.activate and ActiveCell = "x" & ActiveCell and Application.Run "w4bana" 
next i

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim Test As Range
    Dim cl_Target As Range
    Set Test = Intersect(Target, UsedRange)
    If Test Is Nothing Then Exit Sub
    For Each cl_Target In Test
        Select Case cl_Target.Address(0, 0)
        
        Case "L2:L300"
        If cl_Target.Value = 4 Then Call w4bana
        Case "L2:L300"
        If cl_Target.Value = 5 Then Call w5bana
        
         
        Oldvalue = Target
        End Select
        Next
        End Sub

Sub Test()

    Dim lngLastRow As Long
    On Error Resume Next
    lngLastRow = Columns("J").Find(What:="*", LookIn:=xlValues, LookAt:=xlPart, SearchOrder:=xlByRows, _
        SearchDirection:=xlPrevious, MatchCase:=False, SearchFormat:=False).Row
    On Error GoTo 0
    Range("A3:J" & lngLastRow).Select
    Selection.Copy

End Sub

Dim iLastRow As Long
iLastRow = Cells(Rows.Count, "J").End(xlUp).Row
Range("A3:J" & iLastRow).Select