Hi Targa, I'll suggest to set the expression ina table without expression label, this way, setting the mouse on the title you can see how QV is expanding "=$(=(MasterYear-1))", looking this will give you a hint of what's happening.
Maybe is beacuse this is returning null() because MasterYear has more than one possible value, if this is the case you can use:"=$(=(Max(MasterYear)-1))"
The calculation doesn't work if you select more than one year. But it seems that this was not the problem.
Actually, for the complete calculation/analyse (That was only one part from a measure calculation) you would never select more than one year. That would be pointless
So the solution from the russian guy is enough.