How to call the yahoo maps flash api distance method from vb.net?

Hello, I have a web application that I'm using to calculate the distance between two addresses.  I'm able to retrieve the lat and long for the addresses using Yahoo's map API.  How would I calculate the distance between the two lat and long? I've read that there is a distance method in the flash API.  Is this the best way to do this?  If so, can someone help me get started or point me in the right direction?