Error re-running code - vba

Question

firstly, I'm having error running the code from Excel workbook directly. It leads to the error message mentioned below
We looked at all the data next to your selection and didn't see a pattern for filling in values for you. To use Flash Fill, enter a couple of examples of the output you'd like to see, keep the active cell in the column you want filled in and click the Flash Fill button again
However, I could run the code if is played from VBA windows under the developers tab. But Is limited to only 1 run before an error message 1004 pops up and also code error when played again.
Please help. Never taught or learnt VBA in ever. Code below is a mash up of researched on the net and trial & error.
Sub Graph()
'
' Graph Macro
'
' Keyboard Shortcut: Ctrl+e
'
'Select values in a column from specified workbook and sheet
Dim LR As Long, cell As Range, rng As Range
Windows("Area3-LG").Activate
With Sheets("Graph data")
LR = .Range("B" & Rows.Count).End(xlUp).Row
For Each cell In .Range("B4:B" & LR)
If cell.Value <> "" Then
If rng Is Nothing Then
Set rng = cell
Else
Set rng = Union(rng, cell)
End If
End If
Next cell
'Error with rng.select when Macro is runned again
rng.Select
End With
Selection.Copy
'Open next workbook
Windows("InstData_TEMS_Existing").Activate
'Open Sheet L
Sheets("L").Select
'Select empty field fromn column AA
Range("AA" & Rows.Count).End(xlUp).Offset(1).Select
'paste selection to empty field
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
'Go back to previous workbook & delete column
Windows("Area3-LG").Activate
Sheets("Graph data").Select
Columns("B:B").Select
Application.CutCopyMode = False
Selection.Delete Shift:=xlToLeft
Sheets("Graph Data").Select
End Sub
Thanks in advance (:

Answer 1

Try the code below, without all the unnecessary Select, Activate, and Selection:
Sub Graph()
'
' Graph Macro
'
' Keyboard Shortcut: Ctrl+e
'
'Select values in a column from specified workbook and sheet
Dim LR As Long, cell As Range, rng As Range
With Workbooks("Area3-LG").Sheets("Graph data")
LR = .Range("B" & .Rows.Count).End(xlUp).Row
For Each cell In .Range("B4:B" & LR)
If cell.Value <> "" Then
If rng Is Nothing Then
Set rng = cell
Else
Set rng = Union(rng, cell)
End If
End If
Next cell
End With
rng.Copy ' copy the union range (no need to select it first)
' paste without all the selecting
With Windows("InstData_TEMS_Existing").Sheets("L")
' Paste (without select) un the next empty cell fromn column AA
.Range("AA" & .Rows.Count).End(xlUp).Offset(1).PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, _
SkipBlanks:=False, Transpose:=False
End With
Application.CutCopyMode = False
'Go back to previous workbook & delete column
Workbooks("Area3-LG").Sheets("Graph data").Columns("B:B").Delete Shift:=xlToLeft
End Sub