Difference between two ranges

Question

I can find plenty of questions and example regarding the 'Union' and 'Intersect' VBA methods but I can't find anything much regarding a 'Set Difference' method? Does this exist (other than by using combinations of union and intersect)?.

I'm trying to find a simple way of getting all of range1 excluding any of range1 that overlaps range2 without knowing the size or shape of either range.

Any help would be greatly appreciated.

EDIT.

Attempted solution where rng1 is the red section and rng2 is the blue section (have debugged to check these are correct):

rng = SetDifference(rng, highlightedColumns)

Function SetDifference(Rng1 As Range, Rng2 As Range) As Range
On Error Resume Next
If Application.Intersect(Rng1, Rng2).Address <> Rng2.Address Then
    Exit Function
On Error GoTo 0
Dim aCell As Range
For Each aCell In Rng1
    Dim Result As Range
    If Application.Intersect(aCell, Rng2) Is Nothing Then
        Set Result = Union(Result, aCell)
        End If
    Next aCell
Set SetDifference = Result
End If
End Function

Answer 1

Try this function after I have improved it a bit:

Function SetDifference(Rng1 As Range, Rng2 As Range) As Range
On Error Resume Next

If Intersect(Rng1, Rng2) Is Nothing Then
    'if there is no common area then we will set both areas as result
    Set SetDifference = Union(Rng1, Rng2)
    'alternatively
    'set SetDifference = Nothing
    Exit Function
End If

On Error GoTo 0
Dim aCell As Range
For Each aCell In Rng1
    Dim Result As Range
    If Application.Intersect(aCell, Rng2) Is Nothing Then
        If Result Is Nothing Then
            Set Result = aCell
        Else
            Set Result = Union(Result, aCell)
        End If
    End If
Next aCell
Set SetDifference = Result

End Function

Remember to call it like this:

Set Rng = SetDifference(Rng, highlightedColumns)

Answer 2

^Iterating by each cell is very slow for calls like

SetDifference(ActiveSheet.Cells, ActiveSheet.Range("A1")) 'All cells except A1

Therefore:

'(needed by the 2nd function)
Public Function Union(ByRef rng1 As Range, _
                      ByRef rng2 As Range) As Range
    If rng1 Is Nothing Then
        Set Union = rng2
        Exit Function
    End If
    If rng2 Is Nothing Then
        Set Union = rng1
        Exit Function
    End If
    If Not rng1.Worksheet Is rng2.Worksheet Then
        Exit Function
    End If
    Set Union = Application.Union(rng1, rng2)
End Function



Public Function Complement(ByRef rngA As Range, _
                           ByRef rngB As Range) As Range
    Dim rngResult As Range
    Dim rngResultCopy As Range
    Dim rngAreaA As Range
    Dim rngAreaB As Range
    Dim lngX1 As Long
    Dim lngY1 As Long
    Dim lngX2 As Long
    Dim lngY2 As Long
    Dim lngX3 As Long
    Dim lngY3 As Long
    Dim lngX4 As Long
    Dim lngY4 As Long
    Dim lngX5 As Long
    Dim lngY5 As Long
    Dim lngX6 As Long
    Dim lngY6 As Long

    If rngA Is Nothing Then
        Exit Function
    End If
    If rngB Is Nothing Then
        Set Complement = rngA
        Exit Function
    End If
    If Not rngA.Worksheet Is rngB.Worksheet Then
        Exit Function
    End If
    Set rngResult = rngA
    With rngA.Worksheet
        For Each rngAreaB In rngB.Areas
            If rngResult Is Nothing Then
                Exit For
            End If
            lngX3 = rngAreaB.Row
            lngY3 = rngAreaB.Column
            lngX4 = lngX3 + rngAreaB.Rows.Count - 1
            lngY4 = lngY3 + rngAreaB.Columns.Count - 1
            Set rngResultCopy = rngResult
            Set rngResult = Nothing
            For Each rngAreaA In rngResultCopy.Areas
                lngX1 = rngAreaA.Row
                lngY1 = rngAreaA.Column
                lngX2 = lngX1 + rngAreaA.Rows.Count - 1
                lngY2 = lngY1 + rngAreaA.Columns.Count - 1
                If lngX3 > lngX1 Then lngX5 = lngX3 Else lngX5 = lngX1
                If lngY3 > lngY1 Then lngY5 = lngY3 Else lngY5 = lngY1
                If lngX4 > lngX2 Then lngX6 = lngX2 Else lngX6 = lngX4
                If lngY4 > lngY2 Then lngY6 = lngY2 Else lngY6 = lngY4
                If lngX5 <= lngX6 And lngY5 <= lngY6 Then
                    If lngX5 > lngX1 Then
                        Set rngResult = Union(rngResult, .Range(.Cells(lngX1, lngY1), .Cells(lngX5 - 1, lngY2)))
                    End If
                    If lngY5 > lngY1 Then
                        Set rngResult = Union(rngResult, .Range(.Cells(lngX5, lngY1), .Cells(lngX6, lngY5 - 1)))
                    End If
                    If lngY2 > lngY6 Then
                        Set rngResult = Union(rngResult, .Range(.Cells(lngX5, lngY6 + 1), .Cells(lngX6, lngY2)))
                    End If
                    If lngX2 > lngX6 Then
                        Set rngResult = Union(rngResult, .Range(.Cells(lngX6 + 1, lngY1), .Cells(lngX2, lngY2)))
                    End If
                Else
                    Set rngResult = Union(rngResult, rngAreaA)
                End If
            Next rngAreaA
        Next rngAreaB
    End With
    Set Complement = rngResult
End Function