Want to execute a C program from a VisualC++

Hello,
I want to execute a C program from a visual C++ program and wants to retrive the result of execution in the Visual C++ program.I tried to use ShellExecute() and WinExec() funtions.
Eg when i am trying to execute an addition funtion,the result i get in both the above funtions are 2.I don't know whether it is possible to retrieve a result using that method.
What i tried is
int d;
d=(int)ShellExecute(hwnd,"open","C:\path\to\file.exe",NULL,NULL,SW_NORMAL);
Please give a right syntax.
Thankyou.