Sum(Sales) and Sum(Sales) / Sum(Total Sales) assuming you mean the percentage of each department from the global total. Since the Sum(Sales) will be a large value and the percentage will be a small value, you'll need a split axis to do this in a bar chart.
I don't think there's anything to elaborate on regarding the formulas.
Your issue in a bar chart will be that the scale of each value is not similar, so the percentage bar will be tiny compared to the sales bar. I don't remember offhand if the native Qlik bar chart has an option to have two separate Y axis (left and right) or not since I use a third-party extension for bar charts. If it doesn't, you'll want to switch to a combo chart with a secondary axis.
