yes it is possible... but my guess is (and I could be wrong) that you won't find software that you can download to accomplish this. You would have to write it yourself of pay for a custom application.
The main user's mouse clicks and key strokes would be watched (like a key logger infection) by the parent application and it would pass the info on to the children apps to mimic.
If this post of yours is tied in any way to your other thread (Max number of similtaneous IE9 windows?) where you are opening 100 browser windows, then you would need quite a bit of processing power to also control that many windows replicated in other user accounts.
Computer type Laptop System Manufacturer/Model Number Employer provided Dell E6430 OS W7 Pro SP1 64bit CPU i5 3320M @ 2.6GHz Motherboard 0CPWYR Memory 8GB Graphics Card Intel HD Graphics 4000 Screen Resolution 1600 x 900
Hard Drives Samsung SSD 840 Antivirus Employer mandated Symantec Endpoint Protection Browser Pale Moon, IE10 & Chrome. (IE9, IE8 & IE6 via VM)
Possible to run software on multiple useraccounts at same time?