Carry Over values from previous month

Hi,

Just wondering to get some help with regards to my problem.

I am doing a power bi calculation in which will let the first month to have a value of "0" and then carry over the values of the previous months adding the value of the current month.

Ex.

March = 0 or blank
Apr = 0 (from March) + 5 (curr month) = 5
May = 5 (from Apr) + 10 (curr month) = 15
etc...

thanks in advance!