Existence of shapes in Powerpoint - vba

Question

I would like to build a condition on a command button on a Macro enabled powerpoint presentation. If the shape exists then I would like it deleted, otherwise the button should produce a statement about the fact that there is no such shape. Currently I am having trouble with existence...! How do I get Power point to recognise the shape is null? Here is my code:
If ActivePresentation.Slides(3).Shapes("Picture") Is Nothing Then
MsgBox "no Picture"
Else
ActivePresentation.Slides(3).Shapes("Picture").Delete
MsgBox "Picture Cleared"
End If
This code only produces an error because the shape doesn't exist so the first if statement fails. Perhaps we need to check whether its in the selection pane?

Answer 1

Some of the other suggestions will work but in general, it's bad practice to rely on selection unless absolutely necessary. Instead, you could call a slightly different function:
Function ShapeExists(ByVal oSl as Slide, ByVal ShapeName as String) as Boolean
Dim oSh as Shape
For Each oSh in oSl.Shapes
If oSh.Name = ShapeName Then
ShapeExists = True
Exit Function
End If
Next ' Shape
' No shape here, so though it's not strictly necessary:
ShapeExists = False
End Function
You could also modify this to return a reference to the shape if found or nothing if not.
If you prefer not to use early Exit Functions, there are easy ways to write around that.

Answer 2

As #davidmneedham gives in the link in the comments (#TimWilliams answer), you can use a construct similar to as follows:
Option Explicit
Sub test()
Dim shp As Shape
Dim myshapeName As String
myshapeName = "Picture"
Dim sl As Slide
Set sl = ActivePresentation.Slides(1)
If shapePresent(sl, myshapeName) Then
sl.Shapes(myshapeName).Delete
Else
MsgBox myshapeName & " not present"
End If
End Sub
Private Function shapePresent(ByVal sl As Slide, ByVal myshapeName As String) As Boolean
On Error GoTo errhand
sl.Shapes(myshapeName).Select
shapePresent = True
Exit Function
errhand:
shapePresent = False
Err.Clear
End Function
Using the same format as that answer:
Private Function shapePresent(ByVal sl As Slide, ByVal myshapeName As String) As Boolean
Dim myShape As Shape
On Error Resume Next
Set myShape = sl.Shapes(myshapeName)
On Error GoTo 0
shapePresent = Not myShape Is Nothing
End Function