To get the event message number, you have to add 1023 to the custom number. Event pbm_custom01 is 1024, pbm_custom02 is 1025, and so on.
The event can receive the string like this:
String ls_data
ls_data = String(lparam, "address")
The sending program would need this external function declaration:
Function long SendString ( long hWnd, uint Msg, ulong wParam, &
Ref string lParam ) Library "user32.dll" Alias For "SendMessageW"
The code would then be like:
ll_rc = SendString(ll_handle, 1024, 0, ls_message)
I have done this within two objects of the same app for communicating with a "SharedObject" background thread. I have not tried it with a separate process.