Help needed: Calculating SLA only for working hours

Hi all,

I need an help to calculate two days SLA to deliver a report. Here i'm unable calculate only for working hours, currently i'm using below formula for whole two days.

=WORKDAY(A2,2,DATE(YEAR(A2),{12,13},{25,1}))+MOD(A2,1)

What i want achieve is, it should calculate SLA based on my working hours(from 09:00AM to 18:00PM)

Any help would be appreciated!

Elango