I know that it is possible to communicate between Visual Basic and S7-PLCSIM. It had certain limits but I can't remember the details.
Maybe you can write some sort of buffer programm between PLCSIM and your OPC server?
I can send you an example program if you want.
Edit: It appears that the OCX I use is only capable of reading outputs and writing inputs. Or in other words it can only be usefull as a simulation tool.