Calculate working hours

Hi Guys

I have a problem with my project. I have to calculate working hours for given time and date. I have to key in data manually only in cells START TIME, START DATE, TIME/PCS, TOTAL TIME (dd:hh:mm) and OVER TIME. After that, the computer will calculate automatically the COMPLETION TIME, COMPLETION DATE and TODAY WORKING HOURS. The only problem i have to solve is in the COMPLETION TIME because my company have 2 time recess (lunch break and high tea) that i have to consider in my formula. The equation that i already put in the COMPLETION TIME are correct but its only function when TOTAL TIME within 1 day. So that is mean, if TOTAL TIME more that 1 day, ie 3 days, it will not calculate correctly.

For example, you can see in my attachments at row 11. TOTAL TIME are 00:15:00 (15 hours) and START TIME are 8:30 AM. If based of computer's time, it is within 1 day (15 hours less than 24 hours) but if based on my company time, the working hours are 7:30 minutes (7.5 hours), so to finish the TOTAL TIME, it requires 2 days working and the COMPLETION TIME will be 5:30PM but my formula shows 3:30PM.

So, my question is, how to solve the problems? because my formula are working when it only within 1 day but it not shown the correct value when it within more than 1 day. Another factor to consider is the recess time (lunch break and high tea). Probably the time fall before lunch break, between the lunch break or high tea and after high tea (time < |lunch|< time > |high tea| < time). I know, my formula are missing something.

So i hope some of you can help me. Please..

Thanks