[plt-scheme] Shortcuts in message-box/custom?

Hello list,

Is there a way to trigger Button 2 in a message-box/custom with  
command-. and Button 3 with command plus the first letter of the  
button label (e.g. command-D if the button says "Discard" and this  
doesn't conflict with other buttons' names)?

If not, please consider it a feature request. At least command-. for  
cancel is common on OS X, and Cocoa apps usually have shortcuts for  
all three buttons.

Best regards,

Erich