Add the values in one column based on another column.

Harshwardhan  - You will need to have something in your data that defines "previous". See my article on Mean Time Between Failure (MTBF) which uses EARLIER: http://community.powerbi.com/t5/Community-Blog/Mean-Time-Between-Failure-MTBF-and-Power-BI/ba-p/339586

Harshwardhan , to get C2, you need an index or some date column

https://stackoverflow.com/questions/45715963/creating-an-index-column-for-power-bi

Try a new column

sumx(filter(Table, [stockitemname] = earlier([stockitemname]) && [index] <= earlier([index])),[C1])