Highlighting Rows Macro

I understand that but what I am trying to do is highlight the next row. Say I hax an x in row 5, then row 6 will be highlighted. Then when I put an x in row 6 I want row 6 to no longer be highlighted and then row 7 to highlight. I created the event I just need to fix the actual macro. It is as follows (don't know if the firstAddress part does anything):
Event:

Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Range("F4:F200")) Is Nothing Then
Call autoHighlight
End If
End Sub

Macro:

Sub autoHighlight()
Dim rg As Range, c As Range
  Dim firstAddress As String
    Set rg = Range("F4", "F250")
    Application.ScreenUpdating = False
With rg
    Set c = .Find("x", lookat:=xlWhole, LookIn:=xlValues)
    If Not c Is Nothing Then
        firstAddress = c.Address
        Do
            c.EntireRow.Interior.ColorIndex = 6
            Set c = .FindNext(c)
            If c Is Nothing Then Exit Do
        Loop While c.Address <> firstAddress
    End If
Application.ScreenUpdating = True
End With
End Sub