Using SWITCH in a table to evaluate only one row at a time

Hi, so we're trying to visualize changes in a table by adding little arrows, indicating whether an item has moved up or down since yesterday. We have a measure called #arrow that is supposed to indicate whether the arrow should point up, down or sideways. But the arrow always points up, and we suspect this is because the code evaluates the whole table, not just the one row it's on.

The strange thing is that #Test, which is also a measure, does show the correct value for just the one row. We can't figure out why it acts for one row for #Test, but for the entire table for #arrow. We've tried SELECTEDVALUE, VALUES, and SUM for #arrow.

#Test = SUM(X[DeltaRang])

#arrow =
SWITCH(
TRUE(),
SUM(X[DeltaRang]) < 0, UNICHAR(9207), // Negativ
SUM(X[DeltaRang]) = 0, UNICHAR(9205), // Null
SUM(X[DeltaRang]) > 0, UNICHAR(9206), // Positiv
UNICHAR(9210) 
)

Help please?