Looping through controls on a worksheet to set control icons

I am trying to loop through controls on a worksheet to set the mouse icon. It works fine on a form like this:

Sub SetFormControlCursors(form_name As UserForm, cursor_name As String)
    Dim z As Control
    For Each z In form_name.Controls
      If TypeName(z) = "CommandButton" Then
        z.MousePointer = fmMousePointerCustom
        z.MouseIcon = LoadPicture(cursor_name)
      End If
    Next z
End Sub

but adapted for a worksheet, nothing happens:

Sub SetSheetCursors(sheetName As String, cursor_name As String)
    Dim z As Shape
    Dim s As String
    Dim w1 As Worksheet: Set w1 = Sheets(sheetName)
    For Each z In Sheets(sheetName).Shapes
      If TypeName(z) = "CommandButton" Then
        z.MousePointer = fmMousePointerCustom
        z.MouseIcon = LoadPicture(cursor_name)
      End If
    Next z
End Sub

Any ideas why? The controls are Active X command buttons. Thanks!