I need to create a personalized formula in excel?

Im facing this problem, I need to create a personalized formula that helps me to do the next: I got a list of employees that changes every day this is that every single day we have different employees involved in different work orders, at the end of the day I need to calculate the used time in every work order, i do this by adding all the used time Per work order, for example if the employee worked 1 hour in work order number 12345 and 30 minutes in work order number 6789 the total of the day it will be 1 hour 30 minutes, to calculate the time percentage of every work order i divided 1 hour between 1.30 hours this will represent the 77% of the employee time expanded on this work order during the day, my problem is that I have to manually input this formula every single day with every single employee, then I have to calculate the maximum of time and the divided by each work order time subtotal, when there is only like 5 employees during the day is not to complicated or tedious but at the end of the week Is really tedious to do this not to mention the risk of making mistake, again my main problem is that I don't know how to make this easier if creating a personlized formula or with a macro but I would not know the instructions to created, so if anybody have any idea in how to do this please help me, thanks in advance