Dax help

Hello EmilyM2019 

if you need a solution in Power Query, here is the solution

Create a new column and add this formula

if [Customer]="A" then [Working days count] else if [Customer]="B" then [Calendar days count] else "0"

here the complete solution

let
	Source = #table
	(
		{"Working days count","Calendar days count","Customer"},
		{
			{"141","196","A"},	{"72","101","B"},	{"67","94","A"},	{"61","84","C"},	{"54","75","C"},	{"49","68","A"}
		}
	),
    AddCustom = Table.AddColumn
	(
		Source, 
		"Custom", 
		each if [Customer]="A" then [Working days count] else if [Customer]="B" then [Calendar days count] else "0"
	)
in
	AddCustom

Copy paste this code to the advanced editor in a new blank query to see how the solution works. If this solution fits your need, copy and past a part of it and implement it in your query

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Kudoes are nice too

Have fun

Jimmy