Hi Tupai,
Are the two programs running simultaneously, or can the VC++ program launch the CVI program? As a starting point for the former, I would look at the examples in the Example Finder under Communicating with External Applications >> ActiveX << SimpleEventsClient[Server]. Also, there are more examples under the General section of ActiveX.
For the latter, the easiest implementation would be to pass the string as a command-line argument.
Cheers,
David Goldberg
National Instruments
Software R&D