automating Drop vsoSelection to vss file. vsoDoc1.Save '.... leads to MS warning box: "requested operation is presently disabled"

I'm trying to 'polish' the saving of a selected shape to an existing vss file that starts undocked.

I select some shapes:
vsoSelection1.Select MyShape, visSelect
which I wish to drop into vsoDoc1, an undocked vss file:

Set vsoDoc1 =Visio.Documents.OpenEx("C:\Users\Roger\Documents\MyShapes\ExportFromUserFile.vss", visOpenDocked + visOpenCopy)

'the selection is dropped, and then deleted from vst:    
vsoDoc1.Drop vsoSelection1, 0, 0
vsoSelection1.delete
'I want to save and close vsoDoc1, but:    
vsoDoc1.Save '.... leads to MS warning box: "requested operation is presently disabled"
vsoDoc1.Close

Can you please  show me how to save vsoSelection1 to  the named vsoDoc1:
avoiding: MS warning box: "requested operation is presently disabled". Indications of safe practice would be appreciated.

I also need to suppress the Microsoft security dialogue boxes that ask if macros should be enabled or disabled (I need my project macros enabled, and my project vss files accessible). This has security implications. Can you indicate how I should commence understanding my options and asking about best practice?  

Thanks in advance
Kelvin