How to add two values in the same cell of CSV file

I need help to create a csv file with Unix command.

In csv file, i need to put two values in the same cell.

Rite now, whts happening is, if i put 2 values in the same cell, its comming as " asd, zxc" but i want it in different line but in same cell.

asd
zxc

Please reply me ASAP.

Use a newline instead of a comma, a row should be something like:

"value in first cell", "value in second cell 
with separate lines","third cell"