How to attribute pageviews to "most recent" Evar value

I have an evar, lets say evar1, that stores a string, the string has many possible values lets say 'a', 'b', 'c', 'd' etc. As someone moves throughout our website evar1 gets populated with values 'a' then 'b' then 'd'. I want to be able to attribute all pageviews to the most recent or last known evar value per visitor. Right now in evar1 custom reporting it will attribute a pageview to each value regardless of the most recent value. Ultimately this is what i want to see...

Visitor 1:
Navigates to page1, evar1=a,    navigates to page2, evar1=b,    navigates to page3,  evar1=d

then in reporting normally I would see

evar1, pageviews
'a', 1
'b', 1
'd', 1

but I want

evar1, pageviews
'a', 0
'b', 0
d, 3

So the most recent value is what gets counted, I believe I may need to create a custom report but any insights would be greatly appreciated! Thanks!