Set form fields to 'required' based on state

Hi all, I hope you can help me with this one: I have a workflow controlled Item with some properties set as required. When the Item reaches a certain state, some more properties should be made required. Until this state is reached these properties are also hidden, so I can't just make them required on the ItemType, as the user would have no way of entering data into the hidden fields. Showing / hiding the fields on a specific state is achieved using javascript, now I need to set them required, prevent saving the form if they are not filled and paint them blue to indicate they are mandatory. Any help on the matter will be greatly appreciated.   Best regards Carsten