Unable to get formula to subtract 30 minutes for lunch if over 6 hours are worked

I am working on a time sheet and so far I have the formula figured out to add up the hours from the time I input as =TEXT(C1-B1,"h:mm"). The formula I am trying to figure out is if this formula equals 7:00 and I need to subtract 30 minutes if the total is over 6:00 what is my next step. Trying to set up a payroll and need to subtract lunch if a person works over 6 hours. Any help would be greatly apprieciated.