That looks great! So, if I am reading it right, it is saying to add together anything from H and M column, if the label in the J or O column matches what I have already labled in the shopping list (column C). So this is deffinitely the perfect way to get it to add the list up!

However, can this also work before I have any info in the C column? So the formula know that it should EITHER put the item as a new item in column C, OR add it's value to an already existing post?

That's right, do tests.

Decio