Dynamic Chart with Non Continuous data

Hi..this is my first post here, so apologies for any formatting issues..i have attached the relevant file..i have input all the purchases i make as positive numbers and sales as negative numbers...i am trying to create dynamic line charts for different products that i sell..Also, i would need a dynamic chart for the products sold by a specific DSR..i tried using COUNTIF with OFFSET but i am unable to get the same correct..also i am unable to understand how to convert the negative sales numbers to a positive number for charting purposes.. would really appreciate if someone can help me.. thanks a lot