Based on other posts in the thread, I have made the following script fragment for HKN, since my hand is always hovering around the wasd keys I assigned it to the "`" key which on my keyboard is right next to the "1" key

Code:
//-----------------------------------------------------------
// Hotkey: Oem8 Follow the active window 
//-----------------------------------------------------------
<Hotkey Oem8>
    <If ActiveWinIs WoW1>
        <SendLabel w2, w3, w4, w5>
        <Key ctrl Oem6>
    <Else If ActiveWinIs WoW2>
        <SendLabel w1, w3, w4, w5>
        <Key alt Oem6>
    <Else>
        <DoHotKey Hotkey NumLockOn Alt Ctrl Shift Oem8>
    <EndIf>
<Hotkey NumLockOn Alt Ctrl Shift Oem8>
    <If ActiveWinIs WoW3>
        <SendLabel w1, w2, w4, w5>
        <Key shift Oem6>
    <Else If ActiveWinIs WoW4>
        <SendLabel w1, w2, w3, w5>
        <Key ctrl alt Oem6>
    <Else>
        <SendLabel w1, w2, w3, w4>
        <Key ctrl shift Oem6>
    <EndIf>
In WOW I created a character specific macro called "TargetMyFriend"

You can substitute C1, C2, C3, C4 and C5 with your character names.

Character 1 (C1) "TargetMyFriend"

Code:
 
/target [nomod:ctrl,mod:alt,nomod:shift,target=C2] [nomod:ctrl,nomod:alt,mod:shift,target=C3] [mod:ctrl,mod:alt,nomod:shift,target=C4] [nomod:alt,mod:ctrl,mod:shift,target=C5]
Character 2 (C2) "TargetMyFriend"

Code:
 
/target [mod:ctrl,nomod:alt,nomod:shift,target=C1] [nomod:ctrl,nomod:alt,mod:shift,target=C3] [mod:ctrl,mod:alt,nomod:shift,target=C4] [nomod:alt,mod:ctrl,mod:shift,target=C5]
Character 3 (C3) "TargetMyFriend"

Code:
 
/target [mod:ctrl,nomod:alt,nomod:shift,target=C1] [nomod:ctrl,mod:alt,nomod:shift,target=C2] [mod:ctrl,mod:alt,nomod:shift,target=C4] [nomod:alt,mod:ctrl,mod:shift,target=C5]
/follow
Character 4 (C4) "TargetMyFriend"

Code:
 
/target [mod:ctrl,nomod:alt,nomod:shift,target=C1] [nomod:ctrl,mod:alt,nomod:shift,target=C2] [nomod:ctrl,nomod:alt,mod:shift,target=C3] [nomod:alt,mod:ctrl,mod:shift,target=C4]
Character 5 (C5) "TargetMyFriend"

Code:
 
/target [mod:ctrl,nomod:alt,nomod:shift,target=C1] [nomod:ctrl,mod:alt,nomod:shift,target=C2] [nomod:ctrl,nomod:alt,mod:shift,target=C3] [mod:ctrl,mod:alt,nomod:shift,target=C4]
I created a non character specific macro called "RestoreMyTarget"

Code:
 
/notarget
/targetlasttarget
I assign the "TargetMyFriend" macro to MultiBarRightButton1 and the "RestoreMyTarget" macro to MultiBarRightButton2

I then created a non character specific macro called "FollowFriend"

Code:
 
/click MultiBarRightButton1
/follow
/click MultiBarRightButton2
I used the following commands at the console to save the key binding for each "FollowFriend" Macro as the "]" key

Code:
 
/script SetBindingMacro("]", "FollowFriend") 
/script SaveBindings(GetCurrentBindingSet())
Now I can press "`" over the active window to make the other characters follow the active character.

To facilitate spell casting from the background windows I create a macro like the following for each spell.

Code:
 
#showtooltip Frostbolt
/click MultiBarRightButton1
/cast [harm, nodead] Frostbolt; [harm, target=targettarget, exists] Frostbolt
/click MultiBarRightButton2
The following HKN script fragment was required to ensure that the correct key presses were transmitted

Code:
 
<KeyList TheKeyList 0-9, Plus, Minus>
// send the key list to all windows
<Hotkey TheKeyList>
    <If ActiveWinIs WoW1>
        <SendLabel w2, w3, w4, w5>
        <Key ctrl %Trigger%>
        <SendLabel w1>
        <Key %Trigger%>
    <Else If ActiveWinIs WoW2>
        <SendLabel w1, w3, w4, w5>
        <Key alt %Trigger%>
        <SendLabel w2>
        <Key %Trigger%>
    <Else>
        <DoHotKey Hotkey NumLockOn Alt Ctrl Shift %Trigger%>
    <EndIf>
<Hotkey NumLockOn Alt Ctrl Shift TheKeyList>
    <If ActiveWinIs WoW3>
        <SendLabel w1, w2, w4, w5>
        <Key shift %TriggerMainKey%>
        <SendLabel w3>
        <Key %TriggerMainKey%>
    <Else If ActiveWinIs WoW4>
        <SendLabel w1, w2, w3, w5>
        <Key ctrl alt %TriggerMainKey%>
        <SendLabel w4>
        <Key %TriggerMainKey%>
    <Else>
        <SendLabel w1, w2, w3, w4>
        <Key ctrl shift %TriggerMainKey%>
        <SendLabel w5>
        <Key %TriggerMainKey%>
    <EndIf>
Here is the complete HKN script that I use http://pastebin.com/CAqpL7K2

It includes a window swapping mechanism that I use to set the main window, be warned that if you use this script it requires a screen resolution of 2560x1600, it also requires that wow is configured to use a resolution of 720x576. It should be easy enough to alter it for different resolutions, if you do that then make sure you change the position of the indicator icons that are created in the bottom right of the screen to indicate wether active window tracking is enabled or if HotKeys are enabled. You can find the positioning code on lines 170 and 152 of the pastebin script.