Gnome 3.14 keyboard shortcut question

[Tom Ashley <tomashleyjr@gmail.com>]

Greetings,

System: up to date Debian Testing, 64 bit, Gnome 3.14

I'm trying Gnome again after several years of using Fluxbox and need
some help with creating a custom keyboard shortcut.  I'm using 8
workspaces and successfully created keyboard shortcuts for workspaces
1-4 using Settings-> Keyboard->Shortcuts.  Shortcuts for workspaces
5-8 require custom shortcuts.  What is the command to use in creating
these?  I've had no luck finding the answer in the Gnome Help Guides,
by using Google search, or by posting to the Gnome mailing list.  

Thanks in advance for any help.

Tom Ashley