Ah...finally, after I have broken that lengthy formule into 4 function and applied both in excel and outlook for email received 03-04-17 09:00:00 AM and sent 03-04-2017 12:00:00 PM(by creating 3 custom fields - Weekday, Start time, endtime and SLA (weekday - starttime - endtime)/24) the answer in both the excel and outlook is reflecting the correct answer. But in excel when I format the result into [hh]:mm:ss then it is reflecting the correct time. That format part i am unable to do it outlook.
in Excel
1) Result 9 for =(INT((WEEKDAY(A2-2)+B2-A2)/7)*9+INT((WEEKDAY(A2-3)+B2-A2)/7)*9+INT((WEEKDAY(A2-4)+B2-A2)/7)*9+INT((WEEKDAY(A2-5)+B2-A2)/7)*9+INT((WEEKDAY(A2-6)+B2-A2)/7)*9)
2) Result 0 for =(TIME(HOUR(A2),MINUTE(A2),SECOND(A2))-TIME(9,0,0))*24
3) Result 6 for =(TIME(18,0,0)-TIME(HOUR(B2),MINUTE(B2),SECOND(B2)))*24
4) Result 0.125 =(E2-F2-G2)/24
5) Format above result into [hh]:mm:ss and the result is 03:00:ss
In Outlook
1) Result 9 for IIf([Last Verb Exec Type]="None","None",INT((WEEKDAY([Received]-2)+[Last Verb Exec Time]-[Received])/7)*9+INT((WEEKDAY([Received]-3)+[Last Verb Exec Time]-[Received])/7)*9+INT((WEEKDAY([Received]-4)+[Last Verb Exec Time]-[Received])/7)*9+INT((WEEKDAY([Received]-5)+[Last Verb Exec Time]-[Received])/7)*9+INT((WEEKDAY([Received]-6)+[Last Verb Exec Time]-[Received])/7)*9)
2) Result 0 for IIf([Last Verb Exec Type]<>"None",(TimeSerial(Hour([Received]),Minute([Received]),Second([Received]))-TimeSerial(9,0,0))*24)
3) Result 6 for IIf([Last Verb Exec Type]<>"None",(TimeSerial(18,0,0)-TimeSerial(Hour([Last Verb Exec Time]),Minute([Last Verb Exec Time]),Second([Last Verb Exec Time])))*24)
4) Result 0.125 for ([WorkDays]-[Start Time]-[EndTime])/24
5) unable to format :-(