Calculating a measure based on conditional result from another measure

You can either incorporate everything in one single measure or reference your past measures: Whichever works better for your dataset:

Positive Absolute Share Growth = 
var ly_sales = Calculate(SUM(Facts[Sales EURO]), Calendar[Year] = "LY")
var ty_sales = Calculate(SUM(Facts[Sales EURO]), Calendar[Year] = "TY")
var ly_mark_share = DIVIDE(ly_sales, CALCULATE(ly_sales, ALL(Products[Company])))
var ty_mark_share = DIVIDE(ty_sales, CALCULATE(ty_sales, ALL(Products[Company])))
var share__growth = ty_mark_share - ly_mark_share
var total_sales = SUM(Facts[Sales EURO])

return
IF( share_growth > 0, total_sales, 0)

Or:

Positive Absolute Share Growth = 
var share__growth = [Market Share Growth]
var total_sales = SUM(Facts[Sales EURO])

return
IF( share_growth > 0, total_sales, 0)

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Gonçalo Geraldes