Shelling question

I am shelling to another VB program I have written. What I would like to know is how do I make the task ID returned in the Shell call a zero if when I ran the program it was unsuccessful? In otherwords, I know that

VB Code:

MsgBox (Shell("c:\myprogram.exe [url]www.vb-world.com\index.html[/url]"))

will pop up a message box with the programs task ID if it was successful. But, let's say that the program attempted to download a file designated by me in the command line, and it was unsuccessful, how would I get the message box to return a zero?