Excel - variable to apply to active workbook?

Hello Experts,

I have two workbooks - one with a macro and a button to trigger it (wkbk1), and one with data (wkbk2 - it's actually a csv file).  The following works just fine when I run it from within wkbk2:

Dim LR As Long
LR = Range("A" & Rows.Count).End(xlUp).Row
'open the csv file and begin formatting the data
'the following line is commented out when running it from within the csv file
'but is un-commented when I run it from the external workbook
'Workbooks.Open Filename:="F:\Folder\File.csv"

'shift column M to the right
Columns("M:M").Select
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove

'insert formula into M2
Range("M2").Select
ActiveCell.FormulaR1C1 = "=IF(RC[-1]=0,""No"",""Yes"")"

'paste the formula down column M to the last populated cell
Range("M2").AutoFill Destination:=Range("M2:M" & LR)

'copy header from L1 to M1
Range("L1").Select
Selection.Copy
Range("M1").Select
ActiveSheet.Paste
Range("A2").Select

'turn off alerts to save over the existing file
Application.DisplayAlerts = False

'save the csv file as an xlsx file
ChDir "F:\Folder"
ActiveWorkbook.SaveAs Filename:="F:\Folder\File.xlsx", _
FileFormat:=xlOpenXMLWorkbook, CreateBackup:=False

'turn on alerts again
Application.DisplayAlerts = True

'close the workbook
Workbooks("File.xlsx").Close

'exit Excel
Application.Quit

Select allOpen in new window

But I need it to run from another workbook (wkbk1).  However, it places the formula in M2, copies it to M1, and then moves on to the next step (copying the column header from L1 to M1) without pasting the formula down column M.  It appears that LR is based on column A of wkbk1 and not wkbk2.  I need LR to be based on column A in wkbk2, the active workbook, not wkbk1.  

Any help would be greatly appreciated.

I am using Excel 2010 on Windows 7.

Thanks,
J