Create Vacation Rule to Approve the PO in the absence of MD

Hi Experts, hope you all ok .... At our client MD (Top postiion ) is on vacation therefore various notification lying with his account so my one collegue told me we can do the same from create vacation rule but i dont know how does i could be .........??? 
mean while i know the other provision as forward the document and using sys admin to reassign but i want to do the task from the vacation rule ... klindly help me out in this regard plzzzzzzzzzzzzzzz