Calculate Hours Worked After Specific Time

i have a timesheet that we are trying to use. the problem is the column that says shift diff. if an employee works after 6:30pm for 1and 1/2hr, he is entitled to shift hours. shift hours is between 6m and 8am.

As long as he works after 6.30pm but works for at least one and a half hour, he will get the shift.

if work, 9am to 7:30pm, and have break between 2-3pm, should have 1.5hrs shift and 9.5hrs total
if work, 7:45pm-9:45pm, and have break between 8:30-9pm, total hrs work is 1.5 and shift hrs s/b 1.5hrs
if work 3pm to 12am and have break between 7-8pm, total hrs work is 8 and shift hrs s/b 5hrs