Based on your example data, the smallest Measured Value is always for Storage Time = 0, is this always true? If this is the case you can use Col Min
:Measured Value - Col Min(:Measured Value, :Batch, :Temperture)
And if this isn't always the case you need a bit more complicated formula
:Measured Value - Col Min(If(:Storage Time == 0, :Measured Value, .), :Batch, :Temperture)

-Jarmo