I've noticed that there are various guides for boxing multiple characters, but they usually require you to buy a program to send keys to multiple windows at the same time.
If you want a freebie way to do it, and are able to do a touch of logical thinking, you can accomplish the same thing with AutoHotKey.
It can be found here: AutoHotkey - Free Mouse and Keyboard Macro Program with Hotkeys and AutoText
Anyway, once you install the program, all you need to do is make a new text document on your desktop (or wherever) by right-clicking and hitting New then Text Document. Make sure you have the option selected in windows to change file extensions, and name the file NAME.AHK (NAME being whatever the hell you want). It's very important that you are actually changing the file extension name, otherwise what you actually have is a filename that looks like NAME.AHK.TXT, and that won't work.
Open it with Notepad, and insert this line at the top:
Code:
WinGet, wowid, list, World of Warcraft
and save it. Now, you open up however many copies of WoW you are going to run, placing them in the order you want them (for instance, place the copy you will actually be playing on top, then the one you want second underneath, the third underneath the second, and so on). Double click that file and what it will do is parse the windows in the order that you opened them.
Now all you need to do is setup the hotkeys that you want to be sent to all of the other windows by adding the appropriate lines to the NAME.AHK file. For instance, let's say you want all of your characters to jump at the same time, and you are 2 boxing...you would add lines that look like this:
Code:
Space::
KeyWait, Space, D
ControlSend,, {Space}, ahk_id %wowid1%
ControlSend,, {Space}, ahk_id %wowid2%
Return
Make sure when you add or remove lines that you are reloading the script by right click closing the autohotkey icon in your windows tray.
I'll break it down line by line so you understand, and can edit them yourself to make new hotkeys:
Space:: (This is the name of the hotkey, you can make this whatever you want by just changing SPACE to whatever name you want)
KeyWait, Space, D (This tells it what key to look for you to press, in this case SPACE)
ControlSend,, {Space}, ahk_id %wowid1%
ControlSend,, {Space}, ahk_id %wowid2% (These 2 lines are telling it to send the key, in this case SPACE, to each of the window ID's. %wowid1% is the top WoW window, followed by the next one down, and so on. If you have a third WoW instance open, you would add another line identical to these 2, except at the end you would put %wowid3%)
Return (this simply resets it to wait for your next hotkey press)
So, using the above format, if I wanted to add the 1 key to send to all of the windows, I would add lines that look like this:
Code:
1::
KeyWait, 1, D
ControlSend,, 1, ahk_id %wowid1%
ControlSend,, 1, ahk_id %wowid2%
Return
One thing to note is that written word commands (like SHIFT, RETURN, SPACE) need to have the {} brackets like in the first example. For single letters and numbers, the brackets are unnecessary. If you want to add number pad numbers from the right side of your keyboard, you would name them NUMPAD1, and so on. This is handy for making separate keys for your other windows, like being able to chain 3 frost novas one after the other by pressing 1 then 2 then 3, rather than having them all cast at the same time with 1 hotkey.
So, to reiterate, if I were playing 3 characters, and I wanted 1, 2, 3, and SPACE to be sent to all of the windows, my NAME.AHK file would look like this:
Code:
WinGet, wowid, list, World of Warcraft
Space::
KeyWait, Space, D
ControlSend,, {Space}, ahk_id %wowid1%
ControlSend,, {Space}, ahk_id %wowid2%
ControlSend,, {Space}, ahk_id %wowid3%
Return
1::
KeyWait, 1, D
ControlSend,, 1, ahk_id %wowid1%
ControlSend,, 1, ahk_id %wowid2%
ControlSend,, 1, ahk_id %wowid3%
Return
2::
KeyWait, 2, D
ControlSend,, 2, ahk_id %wowid1%
ControlSend,, 2, ahk_id %wowid2%
ControlSend,, 2, ahk_id %wowid3%
Return
3::
KeyWait, 3, D
ControlSend,, 3, ahk_id %wowid1%
ControlSend,, 3, ahk_id %wowid2%
ControlSend,, 3, ahk_id %wowid3%
Return
If you have any trouble, I will attempt to help when I can. I also HIGHLY recommend pawing through the AutoHotKey help file. It is amazingly helpful...I basically learned how to do everything I know with AutoHotKey from the help file.
Anyway, I know it's a touch complicated, but it is easy to learn (and easy to simply modify what I have already given you), and best of all it's a FREE alternative...it just takes a teeny bit of effort.