Add custom validations to restrict date ranges entered for vacation rules ?

Hello

1. Is it possible to add custom validations to restrict date ranges entered for vacation rules to a certain time frame, and how could this be done? (Eg. No longer that 6 months from today).

2. Would it be possible to give user responsibility (AP Invoice Clerk) access to only the Vacation Rules menu under the Administration tab for this Administrator Workflow form?

Would appreciate any help.

Thanks

Len