Call VB external function from a DLL

Hi,

I've developed a C++ DLL that process incoming SMS messages and an EXE VB application that run as a standard program.

How can I call a specific function of EXE VB program from the DLL

I'm trying to develop an SMS filter that receive only messages that come from a specific phone numbers. DLL (MAPIRule) intercept SMS message, call VB program function that check if the phone number is good and return a value to DLL.

Thanks a lot