Selecting a range of varying size based on a condition

Hi,

Basically I have a list of reference codes that I have sorted so that similar reference codes are all sorted together. Now what I want to do is take the standard deviation of a value associated with those reference codes. The thing is that these codes occur in different quantities. I am wondering how to write a forumula for that will only apply to certain cells and will have a range size that I do not know.

Thanks and regards,
Richard

can you share sample file with data..

Here is some sample data. What I want to do is calculate the standard deviation in column A of the volume for each code. The problem is that there are different, unknown numbers of each code.

Cheers!