Thanks for your quick replies. I am interested in knowing how to use PostMessage which is a Windows OS function similiar to SendMessage Thanks Roger

I am presently using WM_COPYDATA and SendMessage to pass string data from a c++ app to my vb.net app. Everything works but the response time gets sluggish in the c++ app waiting for vb.net app to process the message. I would like to use PostMessage to speed up the string data transfer. I read somewhere that I cannot use WM_COPYDATA with PostMessage. How can I use PostMessage to do my data transfer? I would like to see both the vb.net code for receiving data from PostMessage and the c++ code for sending data with PostMessage Will the use of PostMessage really speed up the sending app? Any suggestions , examples or links would be greatly appreciated Roger VS2005 Std / WinXP Pro SP3