ISBoxer has a mouse repeating ability but I don't believe it has the ability to give you mouse movement (other than click to move) on more than 1 character. Even if it did server lag is going to result in some serious frustration as the longer you run the more the characters will seperate, even if they start in the exact same position.
Most boxers use a follow macro and then the arrow (movement) keys to finalize positions or break follow. If you have the basics of ISBoxer down then you just need to pick a "leader selection" method and create a follow macro for it. There are several examples of the basic macros required for of all the methods in the "Macros and Addons" section.

Leader Selection Methods:
Focus Based Hydra (simple to setup, may be slow in PvP when refocusing a new leader, works in raids and for solo play, sacrifices focus in PvE/PvP, though generally not gamebreaking in any respect)
FTL (ISBoxer has a quick setup for this built in, highly versatile but can be a pain to setup initially, great in raids/and for solo play PvE and PvP)
Target/Assist Party Leader (many drawbacks especially when you join a raid wheere you might end up in different parties, easiest setup but you'll probably give it up before you leave the noob zones.)
There are more but these are a few of the most common.