Setting Workbook object I get error '9': subscript out of range - excel

Question

I want to copy information from cells in M79to PAlysis.
My Sub PopulateFields is located in PAlysis.
What is wrong with my reference to a different file?
Sub PopulateFields()
Dim Mur As Workbook, TOMS As Workbook, i As Integer, LastRow As Integer, j As Integer
Set Mur = Workbooks("S:\M\ BPM\M79.xls")
Set TOMS = Workbooks("S:\M\BPM\PAlysis.xlsm")
Set TOMSPos = TOMS.Worksheets("Positions")
Set TOMSAna = TOMS.Worksheets("Analysis")
Set MurexWs = Murex.Worksheets("BB_Overview")
LastRow = Murex.Cells(MurexWs.Rows.Count, 1).End(xlUp).Row
j = 3
For i = 3 To LastRow - 1
If Mur.MurexWs.Cells(i, 2).Value = "Bond" Then
Mur.MurexWs.Cells(j, 6).Copy TOMS.TOMSPos.Cells(i + 1, 1)
j = j + 1
Else
j = j + 2
End If
Next i
End Sub
In the lineSet Mur = ... I get
Error 9: Subscript out of range.

Answer 1

You could use the following to either get an already opened workbook, or open it if it is not opened.
Sub test()
Set mur = GetOrOpenWorkbook("S:\M\BPM\", "M79.xls")
Set toms = GetOrOpenWorkbook("S:\M\BPM\", "PAlysis.xlsm")
End Sub
Public Function GetOrOpenWorkbook(Path As String, Filename As String) As Workbook
'test if workbook is open
On Error Resume Next
Set GetOrOpenWorkbook = Workbooks(Filename)
On Error GoTo 0
'if not try to open it
If GetOrOpenWorkbook Is Nothing Then
Set GetOrOpenWorkbook = Workbooks.Open(Filename:=Path & Filename)
End If
End Function

Answer 2

I assume that you want to open the workbooks: You have to use Workbooks.open. This opens a workbook in Excel (basically the same as opening it via File->Open in Excel)
Set Mur = Workbooks.open("S:\M\ BPM\M79.xls")
(not sure about the space before BPM - check if this is a typo.
If your workbook is already open, the command would be
Set Mur = Workbooks("M79.xls")
This is the syntax for VBA Collections where you can access an object either by (numeric) index or via it's name. The name of a workbook within the Workbooks-collection is the filename, but without the path (this is the reason that you cannot open 2 workbooks with the same name, even if they are stored in different folders).
When you try to access a member of a collection that doesn't exist, VBA will throw the Runtime Error 9.