VB6, Windows 7, dll, inter-process communication, sub-classing, mutex

We need to create an infrastructure for cellular automata (<[login to view URL]>). Basically we need: 1) To create many instances in memory of the same DLL which does some simple processing. 2) We need the central app to be able to access a double precision variable in the dll and 3) We need for any one dll to be able to access that variable in specific other instances which are 'adjacent'. So it's a little like billiards, where one dll receives some force, processes it and then hands the force over to the next one. The central app can query the state of each dll's variable at any time. The code must be thread safe and mutexed and run in Windows 7. When we test it, 50 dlls all running at the same time sending one target dll 1 million increments must leave the target variable of the target dll = 50 million. The code needs to be in vb6 with sub-classing because our staff are business analysts and we'll be copying and pasting with excel.