DSL, Setting Run Custom Tool

Hi everybody, I created a DSL. Every time a create a new file (extension .mydsl) in the debugging instance I need to set manually the Run Custom Tool property associated with this file, so that it generates another file. 

Is is possible having the name of the Run Custom Tool property already set every time I create this kind of file?

Maybe from the code in the DSL?

Regards,

Nico