ExtendScript attachProxy result

Hi,

In the docs, it says ProjectItem.attachProxy() returns 0 when successful.

If I try to attachProxy to a mediaPath that does not exist, Premiere pops up with file not found.

If I try,
var result = attachProxy 

result is always true, even when the mediaPath is not valid. The "file not found" pop-up is suppressed though. 

I suspect my understanding of success is not correct, but basically I just want to try another proxy mediaPath of the initial one does not exist.

Maybe if the attachProxy is true with an invalid mediaPath, I can just use hasProxy() to see if it was successful or not.

thanks