Project Web Access (PWA) changing design

Hi – i am using PWA (Project Web Acces) for time reporting. Is there a way to change the appearance of weekends bzw public hollidays in the task view of PWA? I would like to either change the color or even block wekends and hollidays on PWA – so the system appears more structured.

Is there a tool to do that – or would i have to change the code? i am happy about any hint!

thanks

david