DAX Cumulative less expired

Hi,

I would appreciate some help with DAX.

I am trying to get a Cumulative figure which considers two dates of a Membership. Start and expiry. 

I am able to get a running culmulative figure for start dates however I cannot make it consider expiry dates.

For example if Member A started as a member on 01/01/2017 but expired on 01/05/2017 id expect the cumulative total to be

Month    Members

January   1

February 1

March     1

April       1

May        0

I am using a date table which links date to Start date. Would I be better off having two tables, Start date and expiry date, and linking these dates to the date table, then making a cumulutive of the start minus the cumulative of the expiry?

Any help would be appreciated.

Thanks,