Debugging with zend studio 8 - select local resource

Hi I am trying to debug using Zend studio. When I hit the debug button in firefox, zend asks me to specify the matching local resource. I do this and just when I think I'm getting somewhere it pops up and asks again for the next file and then the next and then the next. I have set the path mapping in the edit server config area but to no avail. Any idea what I need to do?

Any help much ap开发者_StackOverflowpreciated.