With new request parameters (non obsolete definition ) I want to set the start date as today's date and should be greyed out for users to make any changes or atleast should be reset to current date when user selects future or past date

I am using the new obsolete definition with v9.2, I  have 2 requirements - 

1. The start date should be set to today's date and should be greyed out for users to make any changes or atleast should be reset to current date when user selects future or past date.

2. Set 'Valid until' to startdate +7 days (user should not be able to select date > startdate +7 days. I tried solution in of the forum but that isnt working for me.