Run-time error '9': Subscript out of range

[SOLVED]I am trying to run the following code out of my personal workbook. It works on any new workbook I create, but not on any previous workbook (still xlsx) that I open.

Moderator's note: Please take the time to review our rules. There aren't many, and they are all important. Rule #3 requires code tags. I have added them for you this time because you are a new member. --6StringJazzer

Sub HighlightRow()
' Highlight the entire row of the cell selected

Application.ScreenUpdating = False
 
' Remove the Conditional formatting and "screen updating" code from the active sheet (toggle off)   
    For i = 1 To Cells.FormatConditions.Count    ' loops through all conditional formatting rules
        If Cells.FormatConditions(i).Formula1 = "=CELL(""row"")=ROW()" Then
            Cells.FormatConditions(i).Delete
            With ActiveWorkbook.VBProject.VBComponents(ActiveSheet.Name).CodeModule
                On Error GoTo ExitS
                .DeleteLines 1, [5]
            End With
ExitS:
            Exit Sub
            On Error Resume Next
        End If
    Next i
 
' if the above rule is not found, inserts rule and "screen updating" code into activesheet (toggle on)   
    Cells.FormatConditions.Add Type:=xlExpression, Formula1:= _
        "=CELL(""row"")=ROW()"
    Cells.FormatConditions(Cells.FormatConditions.Count).SetFirstPriority
    With Cells.FormatConditions(1).Interior
        .PatternColorIndex = xlAutomatic
        .ThemeColor = xlThemeColorDark1
        .TintAndShade = -0.14996795556505
    End With
    Cells.FormatConditions(1).StopIfTrue = False
    
    With ActiveWorkbook.VBProject.VBComponents(ActiveSheet.Name).CodeModule
        .InsertLines Line:=.CreateEventProc("SelectionChange", "Worksheet") + 1, _
                     String:=vbCrLf & "    application.screenupdating = True"
    End With
    Application.VBE.MainWindow.Visible = False

Application.ScreenUpdating = True

End Sub

Sorry if this is a bit messy. Any help would be appreciated.