Scenario:
To generate a column that will show the Amount for Total Hours a person has worked against his Base Payroll Rate. This calculation should not take into consideration the number of hours for any time off type.

Resolution:
Create a Report with the required columns. In the custom column, provide the below given formula: 

If(ProjectName="<None>",0,totalhours*basepayrollrate)

The above formula takes advantage of the fact that all time off types fall under ' <None> ' Project Name. So whenever the formula encounters no project name, it will not multiply the hours with base pay roll rate.