Difference between results based on slicer selection

Hi George1973 

You did not share a sample of data so I will explain my solution, then you can try it:

1- When you select 2 Items with Slicer the your table will be filtered to show all data for those selected customers 
2- You need to write a measure, so first add a VAR to create a table and add a rank column to it to rank rows based on the customers' names (ADDCOLUMN & RANKX), the output will be the filtered table with a column that has 1 and 2 (first customer and 2nd costumer)
3- then add another VAR (Name it S1) to SUMX a sales when the RANK is 1 (Filter RANK =1)

4- add another VAR to SUMX (Name it S2)a sale when the RANK is 2 (Filter RANK =1)

5- at the end (RETURN) S2-S1

If this post helps, please consider accepting it as the solution to help the other members find it more quickly.
Appreciate your Kudos!!
LinkedIn: www.linkedin.com/in/vahid-dm/

Hi,

First of all, sorry for beeing late with the answer. I have write a measure according to your suggestion and it works fine.

Variance from Selected Companies = 
VAR summary =
    ADDCOLUMNS (ALLSELECTED(Item_Table[Company]), "cCompany", RANKX(ALLSELECTED(Item_Table[Company]),[Grand Total]))
VAR S1=
    CALCULATE([Grand Total],FILTER(summary,[cCompany]=1))
VAR S2=
    CALCULATE([Grand Total],FILTER(summary,[cCompany]=2))
Return
S1-S2

Here is the result:

Thank you very much for assistance.