when agent position is vacant Leave worflow shoudl go to HR Administrator

Hi,

We are using standard leave worflow WS12300111 . Our client requiremnt is if Superior position is vacant (Because of resignation or transfer) leave workflow should automatically routed to HR Administrator of employee (HR administrator is Z relationship in Organizational management) . We are not planning to modify the standard workflow . is there any standard setting or any program which we can use to do this? Please advise me on solution;

Thanks,

Shimal