Support adding mode when doing mirror selection

Question

 I have a  picker that has a command button mirror selection ( pasted from one of your templates ). It is running the following command:

MGP_MirrorSelectViaPanel_Ex

It actually does a flipped selection, ie. if the left side is selected it will select equivalent control on the right side.

The animators want it to select the other side and add it to the selection. Do you have any commands that already do this or should I write my own?

Answer 1

Same rule as Maya, holding the ctrl+shift key when clicking on the button, you are able to add select the mirrored controls.
So basically the MEL procedure ends with _Ex means it might support ctrl+shift modifiers.