DAX Measure - days lost to absence

Hi,

I`m new to DAX and i`m struggling to add a measure. Essentially I have a list of absences for individual employees - please see the "Raw Data" tab. I`v added this to the data model and have created a Power Pivot table with absences summarised by type with days lost. What i would like a measure to do is show the amount of days lost per calendar month. The desired end result would be a chart with a slicer that would show days lost per absence type per month.

Thanks in advance