Change in data; comparing 2 workbooks

Hi I have 2 workbooks from 2 months of sales (see attachment) I would like to identify those opportunities that have moved from one sales stage to another. If sample 0 is last month and sample 1 is this month, how can I identify those opportunities that have changed sales stage but only up until the developing stage???
The data is found in each workbook in a sheet called data
The Sales Stage Name is column F of each data sheet
Opportunities are distinguised by their Opportunity ID, column L
I would like to list the opportunities that have changed from one stage to another in the past month (thus comparing workbook sample 0 to workbook sample 1) and list them in this month's (sample 1) workbook on the sheet named developping opportunities.
Remember only up to the develop stage (thus 2 scenarios possible...(1) Prospect 0% to Qualify 10% or (2) Qualify 10% to Develop 20%. Thank you

Re: Change in data; comparing 2 workbooks

Hey so I modified the formula to fit my workbooks. This Month's Workbook is named 'July 4th,2005 GTM Report', and last month's is named '2005-09-06GTM Report'. The data sheet is actually called 'OPTY fActMgr gGTM Excel'. (I also changed the range to L500 because I have formulas on that sheet starting at 501). When I try to run the macro it says that there is an error. When I try to debug, it tells me that the error is the "orange writting". I have not changed that part of the macro...Any clue as to why this is happening?

Sub Developing_Opts()
'Written by Barrie Davidson
Dim FileToOpen As Variant
Dim LastMonth As Workbook
Dim LookupRange As Range
Dim Comparison As Range

Application.ScreenUpdating = False
FileToOpen = Application.GetOpenFilename("Excel files (*.xls),*.xls", , "2005-09-06GTM Report")
If FileToOpen = False Then Exit Sub
With Sheets("OPTY fActMgr gGTM Excel")
Set Comparison = .Range("M2:M" & .Range("L500").End(xlUp).Row)
End With
Workbooks.Open FileToOpen
Set LastMonth = ActiveWorkbook
With Sheets("OPTY fActMgr gGTM Excel")
Set LookupRange = .Range("L2:L" & .Range("L500").End(xlUp).Row)
End With
Comparison.Formula = "=INDEX([" & LastMonth.Name & _
"]OPTY fActMgr gGTM Excel!" & LookupRange.Offset(, -6).Address & ",MATCH(L2,[" & _
LastMonth.Name & "]OPTY fActMgr gGTM Excel!" & LookupRange.Address & ",0))" Comparison.Value = Comparison.Value
Comparison.TextToColumns DataType:=xlDelimited, _
TextQualifier:=xlDoubleQuote, ConsecutiveDelimiter:=True, Tab:=False, _
Semicolon:=False, Comma:=False, Space:=True, Other:=False, FieldInfo _
:=Array(Array(1, 9), Array(2, 1))

LastMonth.Close False

Comparison.Offset(, 1).Value = Comparison.Offset(, -7).Value
Comparison.Offset(, 1).TextToColumns DataType:=xlDelimited, _
TextQualifier:=xlDoubleQuote, ConsecutiveDelimiter:=True, Tab:=False, _
Semicolon:=False, Comma:=False, Space:=True, Other:=False, FieldInfo _
:=Array(Array(1, 9), Array(2, 1))

Comparison.Offset(, 2).Formula = "=IF(AND(N2-M2>0,N2<=0.2),TRUE,FALSE)"
Comparison.Offset(-1, -12).Resize(Comparison.Rows.Count + 1, 15). _
AutoFilter Field:=15, Criteria1:="TRUE"
Comparison.Offset(-1, -12).Resize(Comparison.Rows.Count + 1, 12). _
SpecialCells(xlCellTypeVisible).Copy _
Destination:=Sheets("Developing Opportunities ").Range("A1")
Comparison.Offset(, -12).Resize(, 15).AutoFilter
Comparison.Resize(, 3).ClearContents
Application.ScreenUpdating = True

End Sub