Adding a mirror staff in an initial script

[Joe Wilkinson]

Hi Richard.

If it is best not to have 7 staffs, the last 4 mirrored, and change the 
Key/Time Signatures on loading because their mirror status needs 
changing by hand afterwards,

And it is better to start off with the top 3 and add the remaining 4 
dynamically,

I am struggling with how. If I use:
;;AddMirrorStaff
(d-AddMirrorVoice 'staff)

the staff is added but I have to choose its parent by hand: I'd like to 
be able to specify by name, or "Staff1" etc. Is that possible?

'staff seems to be a dummy parameter; I can replace it with 
'anything-starting-apostrophe and it works

Joe