Calculating Net Working Hours.

Will the ticket always be created within the business hours? If so then with ticket start time/date in A2 try this formula to get the time that it must be completed

=WORKDAY(A2,5)+MOD(A2,1)

format to show date and time

Note: unless you're using Excel 2007 then WORKDAY is part of Analysis ToolPak add-in, you may have to enable this

No, ticket can be cteated at any time.