Adding One-off cost to a Rolling Cost Measure

[Nir0]

Hi,

I am currently trying to figure out a way to add a one-off cost to a rolling cost measure.

To give a better idea: Vehicle Hire

It will have a daily hire cost, but some times you may be charged a one-off cost (ie. installation fee).

I have created a measure where it calculates the Year to Date cost and also Monthly Cost, which changes accordingly to a date slicer, but everytime I try to add the one-off cost, it does not return the correct figure.

I've also just tested out to see if the one off cost comes up correctly which it does, does anyone know of a way which I can get it to work?

Thanks

[Anonymous]

Please give some sample data, table, images. It would help also if you tried to explain the logic of this measure in DAX-like terms, even if incorrect, this will help us understand the desired funcitonality.