OOB way to add 'n' field rows onto CRM form

Hi -

My requirement is in such a way, it should allow users to add new row (stay with me!) of fields on a particular section/grid to follow the first row. Also, allow them to keep adding new row(s) (which has say 3 fields).

Kind of like, after filling the first row if the user wants to add more info onto next row, select-a-value/click-a-button to see new row.

It is vital for me to know the best & feasible OOB way to accomplish this? Because trailing which we have some Business Rules doing some calculations cumulatively.

Thanks in advance!

- Ankush