How to set a Valid To Time for a Role

Hi,

Is there a way to set a 'Valid To' Time for a User Role Assignment.

I know there is a 'Valid To' Date field in SU01. But we need to expire a few Role Assignment at a particular time of the Day.

But we are looking for a 'Valid To' Time as well, along with the Date. We may create a Z TCode for this but what I want to know is there a Function Module which can be used or any other Inputs?

Thanks!