I want to create a macro that checks the notes master for existing
placeholders and adds only those placeholders (of the six available) that do
not already exist.  

I am able to delete all placeholders and then create all placeholders, but
then the slides do not automatically reflect the formatting of the newly
added placeholders. Yes, I could reapply the master to all slides but that
messes with the formatting inside the body text box (my tabs and indentation
settings get lost).

I know how to check the type of a placeholder and then do something if it is
(or is not) a specific type (such as ppPlaceholderBody). But I can't figure
out how to "take attendance".  Is there some sort of "if this placeholder
format is/is not represented on this notes master then..." routine/structure
I can use?

I have searched http://www.pptfaq.com (and the Internet in general) but
can't seem to find quite what I need. I'm hoping someone has done something
like this before and can point me to an example. If not, then a hint as to
how to approach this would help too.