Purchase Requistion Relase Date as System Date.

Dear Experts,

I need some information on purchase requisitions.

1.our users are changing release date manually the date which they are releasing the Purchase requisition.

can we make the release date as system date,what type of configuration i needed to do that..

2.mass un release of purchase requisitions.

3.mass deletion of purchase requisition and mass deletion of purchase requisition line items

please suggest me

Thanks in advance

Regards,

Varun