Function changes value in sheet - excel

Question

I am creating a function which prototype is:
Function TableToText(ByVal Table As Range) As String
This function is supposed to give me a string and not modify the sheet at all. However the operations that I perform on Table (which is a Range) inside the function also modify my sheet.
I thought ByVal which is the default was supposed to prevent that?
I tried in my function to make another range but to make another Range you use Set so it wouldn't have solved the problem anyway...
Can someone point out what I am missing here? Thank you in advance! :)
The whole function is
Function TableToText(Table As Range) As String
Dim nbColumns As Integer, nbRows As Integer
Dim i As Integer, j As Integer, s As Integer
Dim max As Integer, difference As Integer
nbColumns = Table.Columns.Count
nbRows = Table.Rows.Count
With Table
'' adding the spaces
For j = 1 To nbColumns
max = 0
' Find the longest string in the column
For i = 1 To nbRows
If Len(.Cells(i, j).Value) > max Then
max = Len(.Cells(i, j).Value)
End If
Next i
' Adding the spaces and the |
For i = 1 To nbRows
If Len(.Cells(i, j).Value) < max Then
difference = max - Len(.Cells(i, j).Value)
For s = 1 To difference
.Cells(i, j) = CStr(.Cells(i, j).Value) + " "
Next s
End If
.Cells(i, j) = CStr(.Cells(i, j).Value) + "|"
Next i
Next j
'' Creating the plain text table string
For i = 1 To nbRows
For j = 1 To nbColumns
TableToText = TableToText + .Cells(i, j).Value
Next j
TableToText = TableToText & vbCrLf
Next i
End With
End Function

Answer 1

There's a lot of misleading information and confusion on this page.
I thought ByVal which is the default was supposed to prevent that?
The default is ByRef in VBA. This is unfortunate, because the vast majority of the time, what you mean to do is to pass things ByVal.
Objects are always passed by reference [...] ByVal is ignored.
No. Objects are never "passed", period. What's passed byref/byval is a reference to the object, i.e. a pointer. That does not mean object parameters are always passed ByRef at all.
Let's debunk this claim once and for all.
Public Sub DebunkObjectsAreAlwaysPassedByRefClaim()
Dim thing As Collection 'any object type will do
Set thing = New Collection
DoSomethingByVal thing 'we pass a COPY of the pointer
Debug.Print thing.Count 'no problems here
DoSomethingByRef thing 'we pass a reference to our local pointer; what could possibly go wrong?
Debug.Print thing.Count 'error 91! the object reference is gone!
End Sub
Private Sub DoSomethingByVal(ByVal o As Object)
Set o = Nothing 'affects the local copy only
End Sub
Private Sub DoSomethingByRef(ByRef o As Object)
Set o = Nothing 'affects the same object pointer the caller gave us. this is bad.
End Sub
ByRef vs ByVal makes a major difference: give a procedure your object pointer (ByRef), and they can do anything they like with it - including Set-assigning it to a completely different object reference, or making it Nothing. Give a procedure a copy of your object pointer (ByVal), and whatever they do with it (including Set-assigning it to a completely different object reference or making it Nothing) will only affect that copy.
In both cases, whether you've passed the pointer itself or a copy of it, either way you're giving the procedure access to the same object, so as GSerg explained, any instruction that affects a Range (which you can't create - all Range objects belong to Excel, all you ever get is a pointer to one), regardless of where the pointer comes from, will affect the Range instance state.
So if you don't want to affect any worksheet, don't affect any Range and work with arrays instead.

Answer 2

Objects are always passed by reference even if you specify the byval keyword.
You should use a temporary array to store your values.
For example, something like that :
Function TableToText(Table As Range) As String
Dim nbColumns As Integer, nbRows As Integer
Dim i As Integer, j As Integer, s As Integer
Dim max As Integer, difference As Integer
nbColumns = Table.Columns.Count
nbRows = Table.Rows.Count
Dim tmpValues(nbRows, nbColumns) As String
With Table
'' adding the spaces
For j = 1 To nbColumns
max = 0
' Find the longest string in the column
For i = 1 To nbRows
If Len(.Cells(i, j).Value) > max Then
max = Len(.Cells(i, j).Value)
End If
Next i
' Adding the spaces and the |
For i = 1 To nbRows
If Len(.Cells(i, j).Value) < max Then
difference = max - Len(.Cells(i, j).Value)
For s = 1 To difference
tmpValues(i, j) = CStr(.Cells(i, j).Value) + " "
Next s
End If
tempValues(i, j) = CStr(.Cells(i, j).Value) + "|"
Next i
Next j
'' Creating the plain text table string
For i = 1 To nbRows
For j = 1 To nbColumns
TableToText = TableToText + tmpValues(i, j)
Next j
TableToText = TableToText & vbCrLf
Next i
End With
End Function
Hope it helps.