I'd like to create a spreadsheet where I can calculate when a time period will end by adding a certain number of time periods to a base time. For instance, The base time (starting time)I wish to use is 9:30 a.m. I wish to add 15 minute time periods to the base time. For this example, I'll randomly choose 43 time periods. 

There are 27 15 minute periods in the day. (Starting at 9:30 a.m and ending at 4:15 p.m.) If I have cell A1 Filled with the 9:30 a.m. starting time and cell B1 filled with the integer 43 how could I compute the ending time in cell C1?
Let's say the day I need to start from Tuesday, so the starting time is 9:30 A.M. on a Tuesday. 

I don't wish to include weekend days and I don't wish to include time periods outside the 9:30 a.m. to 4:15 p.m. time frame.

I can do the math on paper seeing the 43rd period will end at 1:30 p.m. Thursday. (43 periods minus 27 periods per day = 16 periods. 16 15 minute periods is 4 hours. 4 hours from 9:30 a.m. is 1:30 p.m.)

Anybody willing to help me code this?