Select All Unlocked Cells On Sheet

I am trying to select all unlock cells in the active sheet. However, my method checks through each cell in the sheet and it takes too long.


Sub SelectUnlockedCells()
Dim rng As Range

If IsNull(Cells.Locked) Then
'if null then there is unlocked cells
For Each c In cells
If c.Locked = False Then
If rng Is Nothing Then
Set rng = c
Else
Set rng = Union(rng, c)
End If
End If
Next c
Else
End If

If rng Is Nothing Then Exit Sub

rng.Select

End Sub