Eclipse can't find RLD file   

I'm trying to execute a transformation programatically from within an eclipse plugin and I get an exception when I try and load the .rdl file:

MappingDefinition def = MappingDefinitionLoader.getApplicationLoader().loadFile("file.rdl");

There's a good reason for the file not found exception I get and that's because it's looking for the file in S:\Eclipse which is my eclipse directory, not in the place where it actually is which is my project directory (S:\Eclipse-WS\project-name).

Any ideas what could be going wrong?

Thanks,

Chris