How to pay AP expense report in current time when expense report created with future date

Dear AP Expense Report Guru,

We have a requirement and I would like to know any of you have this requirement in the past and if you were able to find solution for it.

We have certain AP Expense Reports that our staff create for their future business traveling. However, we would like such AP Expense Report be paid like real time once they submit the expense report. However, keep their AP expense Report invoice as the same future actual travel/conference date.

Example:

   Conference in CA on 9/10/2016 ----> The Expense Report date should have 9/10/2016 as AP invoice date.

The actual Plain & Registration was purchased on 5/27/2016.