alternative formula

I have a work book that contains dates; time entries; paid leaves and official business trips; tardy and under time. I would like to compute for the tardy of an individual and disregard the break time. here's the condition:

1.start time is 8:30am;
2.break time is 12:30pm to 1:30pm
3.end time is 5:30pm
4.can determine the weekends (Saturdays and Sunday)
5.from the tardy or under time it subtracts the value of 4.00 for am and or 4.00 for pm from different columns.

What formula that will suits this conditions without using the vb?

any idea and suggestions is appreciated.

Thank you so much for the time and help.