Yes, Sjors is right. That is the best solution
The following documentation will guide you in a right path in terms of creating entity and microflows.
Create one entity with different attributes for all your inputboxes and one attribute for your result.
Place a dataview on the page with this entity as parameter. In this dataview (or in the footer) place your microflow button. Your entity should now be available as inputparameter for this microflow, where you can use all the attributes for your calculations. This is done by adding actions in your microflow, for instance ‘create varabiable’ or ‘change object’. Make sure to check for empty values to not get any unexpected bugs ;)
Place all these input textboxes inside dataview and create one entity, add attributes to those entities then, select this entity as a datasource for this dataview. for calculation button you can select a onclick event as a call a microflow, the microflow in which calculation logic is done.
hope so it will give you results.