Hi Al,
As said the button is placed inside the A1 dataview and on click of this you are calling a microflow. So the microflow will have the parameter of type A1. You can retrieve the values from entity B1,B2, B3 using Retrieve action with some xpath condition.
Consider B1 entity has attribute result which is of type decimal.
Now, create a variable of type result in the microflow and inside it do the multiplication using the attributes available.
Eg:
Now, Change the object B1 and assign this variable value to result attribute.
Finally show page and pass this object and display the result in that page. Hope this might help.
Thanks.
Regards
Sushuma.