Código:
Sub ResaltarErrores()
Dim Rng As Range
Dim C As Integer
For Each Rng In ActiveSheet.UsedRange
If WorksheetFunction.IsError(Rng) Then
C = C + 1
Rng.Interior.Color = 13551615
End If
Next Rng
MsgBox "Se han encontrado un total " & C & " error/es."
End Sub