Dax Measure

Hello Community, 

I am really hitting a road block so any help will be really appreciated.

I have a sample table as below:

Taking "Bob" as an example, in the PowerBI, I would have a Pivot table that looks like below: 

(As the example below, it contains a Drill down in rows, Month then Name)

The first measure I need - demostrated as "Calulation A"

Formula for Calculation A:   

(Total Hours worked by Bob * Total Percent of work done by Bob)/Total Hours work by "Everyone")

As for Bob in Calculation A:

(8*0.81)/25

Here is where I am stuck - The desired table has no names as part of the row drill down but only months but I need the calculation to stay in groups base on its name. 

The most difficult part is, when multilple names are selected (Names is part of the slicer selection), 

the calculation becomes as follow: 

(0.2592*8/25)+(0.1216*4/25)+(0.1752*6)/0.73+0.1904*7/25 = Final Answer

Basically, Calculation A (measure) needs to times the total work hour of that person itself again

then divide the total work hours by everyone

then add all the person's individual result all together

to get my final answer in that work month. 

Sorry, it sounds very complicated and it is very complicated and hard so I am very stuck becasuse I thought I could use group by but group by doesn't work either. Any possible ways to solve this would be highly appreciated.

Thank you!