Excel 2010: Subscript out of range error - vba

Question

The error that I am receiving is Run-time error '9': Subscript out of range.
Sub Workbook_Open()
'Turn off any alerts that maybe displayed.
Application.DisplayAlerts = False
'Turn of the screen updates
Application.ScreenUpdating = False
'Declare the workbook, create it, save it and close it
Dim wk As Workbook
Set wk = Workbooks.Add
wk.SaveAs Filename:="C:\Saved File\KPI_Grid.xlsm", FileFormat:=52, Password:="", WriteResPassword:="", _
ReadOnlyRecommended:=False, CreateBackup:=False
wk.Close
'Open the workbook again. This will get rid of the 'Compatibilty View' and then activate the orginal workbook
Application.Workbooks.Open Filename:="C:\Saved File\KPI_Grid.xlsm"
Workbooks("KPI Grid V5K1 - macro testing.xlsm").Activate
Worksheets("Weekly").Activate
'Select all cells and copy them
Cells.Select
Selection.Copy
'Activate the workbook and sheet that we are going to paste into.
Workbooks("KPI_Grid.xlsm").Activate
Worksheets("Sheet1").Activate ' ******************ERROR HERE ******************
Cells.Select
Selection.PasteSpecial Paste:=xlPasteAllUsingSourceTheme, Operation:=xlNone _
, SkipBlanks:=False, Transpose:=False
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
'Activate the previous workbook again.
Workbooks("KPI Grid V5k1 - macro testing.xlsm").Activate
Worksheets("Monthly").Activate
Cells.Select
Cells.Copy
Workbooks("KPI_Grid.xlsm").Activate
Worksheets("Sheet2").Activate
Cells.Select
Selection.PasteSpecial Paste:=xlPasteAllUsingSourceTheme, Operation:=xlNone _
, SkipBlanks:=False, Transpose:=False
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
End Sub
I thought this was a relatively simple task.
The aim is to create a new workbook, copy the values of two sheets over and then save and close the new workbook.
Why does this code error?

Answer 1

Go to this line Worksheets("Sheet1").Activate
Press F9
Press F5
Check the screen - has the workbook "KPI_Grid.xlsm" been activated ?
Does it actually have a sheet called "Sheet1" ?
If Sheet1 is not in the same workbook as the code then this will naturally error - you need to ensure everything is qualified like this:
ActiveWorkbook.Worksheet("Sheet1").Activate