Semi-Additive Measures / Last Value

Hi, How can we calculate semi additive measures i.e. measures that cannot be aggregated across time but can be aggregated across other dimensions?

I have a usecase for client account balances which for obvious reasons can’t be added together across time so I’d like to construct a measure theat returns the last value for the given slice / tuple of the data. Your help would be greatly appreciated.

Thanks,
Mark