QueryValue to find Preview application

[rjpwilliams]

I have used QueryValue widely in Access to determine the application associated with a given extension:
Example:
If sExtension = "jpg" Then
sExtension = "jpeg"
End If
If blViewOnly Then
sOpenString = QueryValue(HKEY_CLASSES_ROOT, QueryValue(HKEY_CLASSES_ROOT, "." & sExtension, "") & "\Shell\Open\Command", "")
End If

However, I need to find the application not for Open but for Preview. I could use Shell, but I want to check to see if the application is open first before using shell to call it. Any way of finding it using QueryValue.