When building a graph the same principles as in a calculation field are used - you can divide, multiply, add or subtract different input widgets such as sliders (S*(number)), checkboxes (B*(number)) and input (N*(number)).
Below is an example of a pie diagram using sliders to determine the values.
When selecting the graph, you see the names of all widgets that are taken into calculation.
Hereafter you can select the specific section of the pie diagram. In this example the grey section is selected:
Note the yellow marked value field: the calculation can be typed in here. In this example slider H1_S1 (H1 is for hotspot number 1) is multiplied by the slider H1_S2.