Formula to Calculate Quarter & Yearly Figures

Hi, i'm busy building a sales dashboard but I got stuck with a formula to group information together. I have all the information in a workbook called INPUT. Now I have another workbook which I call CALCULATIONS and this is where I do all the cals. I want to calculate the following, ie ColB - name of sales persons, ColZ - margin. I want to calculate all the margin per sales person. I have tried dsum but no luck. Thanks