Excel 2007 : help in creating a pivot custom formula (sum of collections / count of accounts)

Basically I am having difficulties in creating a summary in pivot. I used to do this formula when I was still in the company but since I have left and do not get to use excel that much any more I have already forgotten how to do it.

A friend has asked me recently to create a template and am now stuck. To make the short story shorter, here is a sample;

smple.xlsx

If any one can help, I would really appreciate it.

I just remembered what to do. For those that have the same problem, just create a column in SOURCE DATA and put value as one. You can now divide the total sales (sum of sales) and the sum of the unit count.