Option Explicit
' Returns Rng1 Minus Rng2
Function RngMinusRng(ByVal rng1 As Range, ByVal rng2 As Range) As Range
    Dim r As Range, ra As Range, r2 As Range
    Dim nrows As Long, ncols As Long, i As Long, j As Long

    With rng1.Parent
        nrows = .Rows.Count
        ncols = .Columns.Count

        Set RngMinusRng = rng1
        Set r = Intersect(rng1, rng2)
        If r Is Nothing Then                          ' диапазоны не пересекаются
            Exit Function
        End If

        For Each ra In r.Areas
            Set r2 = Nothing
            i = ra.Row + ra.Rows.Count
            j = ra.Column + ra.Columns.Count
            If ra.Column > 1 Then Set r2 = Union2(r2, .Range(.Cells(1, 1), .Cells(nrows, ra.Column - 1)))
            If ra.Row > 1 Then Set r2 = Union2(r2, .Range(.Cells(1, ra.Column), .Cells(ra.Row - 1, ncols)))
            If j <= ncols Then Set r2 = Union2(r2, .Range(.Cells(ra.Row, j), .Cells(i - 1, ncols)))
            If i <= nrows Then Set r2 = Union2(r2, .Range(.Cells(i, ra.Column), .Cells(nrows, ncols)))

            Set RngMinusRng = Intersect(RngMinusRng, r2)
        Next ra

    End With
End Function

Private Function Union2(r1 As Range, r2 As Range) As Range
    If r1 Is Nothing Then
        Set Union2 = r2
    Else
        Set Union2 = Union(r1, r2)
    End If
End Function

' Вычитает из UsedRange Selection и отображает цветoм
Sub test()
    Dim r As Range, ra As Range
    With ActiveSheet.Cells.Interior
        .Pattern = xlNone: .TintAndShade = 0: .PatternTintAndShade = 0
    End With

    RngMinusRng(Selection.Parent.UsedRange, Selection).Interior.Color = vbYellow
End Sub