change calculating with the selected data

hi!

some times ago i`m need calculate the measure

"share on cumulative total"(4-th columns on pictures)

then i`m don`t selected anyone, all worked correctly (basic share=1), but on selection any foreign filter, basic share calculated incorrectly (less then 1).

 for the correct accounts, i need change formula`s of account

how me , using IF, 
input  all variants in formula?

 



thanks