I am using Chip Pearsons recommended code snippet to see
if a cell is circular:

If Not Application.Intersect(rng, rng.Precedents) Is
Nothing Then
CellIsCircular = True
End If

However it fails when it comes across a cell which does
not have a formula. So I added a test for a formula:

If rng.HasFormula = True Then
If Not Application.Intersect(rng, rng.Precedents) Is
Nothing Then
CellIsCircular = True
Else
CellIsCircular = False
End If
End If
End Function

However it seems to fail when indeed there is a precedent
but not on the same sheet as the cell. Is this becauase
the precedent property on list precedents on the same
sheet as the cell in question?