Customizing kdp skin using css

I have downloaded the kdp_v2.6.2 project and I have customized the kdp_skin_aps_v5.css file to skin my player. I can build the project and get the kdp_skin_aps_v5.swf file. But, if I change the name of the .css file (like "my_skin.css"), I can't build the project.

I can't find the config file where is set the .css file default value to "kdp_skin_aps_v5.css"

any suggestions?

thanks